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	$174.96	9.258%	$191.1578	$191.16	$191.15	$191.20
Purchase #2	$86.69	9.440%	$94.8735	$94.87	$94.85	$94.90
Purchase #3	$190.54	13.629%	$216.5087	$216.51	$216.50	$216.50
Purchase #4	$106.58	4.695%	$111.5839	$111.58	$111.60	$111.60
Purchase #5	$250.65	13.227%	$283.8035	$283.80	$283.80	$283.80
Purchase #6	$170.42	8.683%	$185.2176	$185.22	$185.20	$185.20
Purchase #7	$71.63	13.838%	$81.5422	$81.54	$81.55	$81.50
7 purchase totals =	$1,051.47		$1,164.6872	$1,164.68	$1,164.65	$1,164.70