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	$101.83	7.715%	$109.6862	$109.69	$109.70	$109.70
Purchase #2	$161.83	6.199%	$171.8618	$171.86	$171.85	$171.90
Purchase #3	$76.35	3.702%	$79.1765	$79.18	$79.20	$79.20
Purchase #4	$55.37	10.364%	$61.1085	$61.11	$61.10	$61.10
Purchase #5	$65.83	3.204%	$67.9392	$67.94	$67.95	$67.90
Purchase #6	$94.58	13.290%	$107.1497	$107.15	$107.15	$107.10
Purchase #7	$32.65	3.703%	$33.859	$33.86	$33.85	$33.90
7 purchase totals =	$588.44		$630.7809	$630.79	$630.80	$630.80