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	$107.66	6.683%	$114.8549	$114.85	$114.85	$114.90
Purchase #2	$20.28	7.872%	$21.8764	$21.88	$21.90	$21.90
Purchase #3	$86.36	5.150%	$90.8075	$90.81	$90.80	$90.80
Purchase #4	$63.85	12.770%	$72.0036	$72.00	$72.00	$72.00
Purchase #5	$44.76	4.696%	$46.8619	$46.86	$46.85	$46.90
Purchase #6	$113.89	4.249%	$118.7292	$118.73	$118.75	$118.70
Purchase #7	$86.80	10.840%	$96.2091	$96.21	$96.20	$96.20
7 purchase totals =	$523.60		$561.3426	$561.34	$561.35	$561.40