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	$73.77	13.721%	$83.892	$83.89	$83.90	$83.90
Purchase #2	$61.96	13.377%	$70.2484	$70.25	$70.25	$70.20
Purchase #3	$86.64	10.286%	$95.5518	$95.55	$95.55	$95.60
Purchase #4	$13.61	11.374%	$15.158	$15.16	$15.15	$15.20
Purchase #5	$57.83	11.419%	$64.4336	$64.43	$64.45	$64.40
Purchase #6	$71.79	4.663%	$75.1376	$75.14	$75.15	$75.10
Purchase #7	$134.25	12.677%	$151.2689	$151.27	$151.25	$151.30
7 purchase totals =	$499.85		$555.6903	$555.69	$555.70	$555.70