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	$64.87	10.716%	$71.8215	$71.82	$71.80	$71.80
Purchase #2	$136.57	3.304%	$141.0823	$141.08	$141.10	$141.10
Purchase #3	$203.72	10.852%	$225.8277	$225.83	$225.85	$225.80
Purchase #4	$55.59	6.589%	$59.2528	$59.25	$59.25	$59.30
Purchase #5	$28.59	9.158%	$31.2083	$31.21	$31.20	$31.20
Purchase #6	$85.29	13.157%	$96.5116	$96.51	$96.50	$96.50
Purchase #7	$222.32	9.648%	$243.7694	$243.77	$243.75	$243.80
7 purchase totals =	$796.95		$869.4736	$869.47	$869.45	$869.50