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	$57.81	5.844%	$61.1884	$61.19	$61.20	$61.20
Purchase #2	$237.52	7.834%	$256.1273	$256.13	$256.15	$256.10
Purchase #3	$81.91	9.144%	$89.3999	$89.40	$89.40	$89.40
Purchase #4	$62.40	10.252%	$68.7972	$68.80	$68.80	$68.80
Purchase #5	$61.25	4.760%	$64.1655	$64.17	$64.15	$64.20
Purchase #6	$95.92	3.757%	$99.5237	$99.52	$99.50	$99.50
Purchase #7	$82.52	13.502%	$93.6619	$93.66	$93.65	$93.70
7 purchase totals =	$679.33		$732.8639	$732.87	$732.85	$732.90