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	$134.52	8.617%	$146.1116	$146.11	$146.10	$146.10
Purchase #2	$150.90	11.213%	$167.8204	$167.82	$167.80	$167.80
Purchase #3	$53.32	7.548%	$57.3446	$57.34	$57.35	$57.30
Purchase #4	$182.51	9.491%	$199.832	$199.83	$199.85	$199.80
Purchase #5	$227.80	6.318%	$242.1924	$242.19	$242.20	$242.20
Purchase #6	$56.44	5.443%	$59.512	$59.51	$59.50	$59.50
Purchase #7	$91.35	9.759%	$100.2648	$100.26	$100.25	$100.30
7 purchase totals =	$896.84		$973.0778	$973.06	$973.05	$973.00