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	$123.41	5.117%	$129.7249	$129.72	$129.70	$129.70
Purchase #2	$16.58	11.733%	$18.5253	$18.53	$18.55	$18.50
Purchase #3	$89.89	5.712%	$95.0245	$95.02	$95.00	$95.00
Purchase #4	$8.59	5.417%	$9.0553	$9.06	$9.05	$9.10
Purchase #5	$56.94	12.581%	$64.1036	$64.10	$64.10	$64.10
Purchase #6	$174.83	12.300%	$196.3341	$196.33	$196.35	$196.30
Purchase #7	$52.86	5.175%	$55.5955	$55.60	$55.60	$55.60
7 purchase totals =	$523.10		$568.3632	$568.36	$568.35	$568.30