Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$200.74	10.591%	$222.0004	$222.00	$222.00	$222.00
Purchase #2	$137.94	9.379%	$150.8774	$150.88	$150.90	$150.90
Purchase #3	$123.29	13.250%	$139.6259	$139.63	$139.65	$139.60
Purchase #4	$91.80	12.749%	$103.5036	$103.50	$103.50	$103.50
Purchase #5	$153.28	5.529%	$161.7549	$161.75	$161.75	$161.80
Purchase #6	$166.34	13.587%	$188.9406	$188.94	$188.95	$188.90
Purchase #7	$167.44	10.771%	$185.475	$185.48	$185.50	$185.50
7 purchase totals =	$1,040.83		$1,152.1778	$1,152.18	$1,152.25	$1,152.20