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	$131.83	11.733%	$147.2976	$147.30	$147.30	$147.30
Purchase #2	$81.80	9.637%	$89.6831	$89.68	$89.70	$89.70
Purchase #3	$33.43	5.304%	$35.2031	$35.20	$35.20	$35.20
Purchase #4	$63.28	13.153%	$71.6032	$71.60	$71.60	$71.60
Purchase #5	$120.27	9.361%	$131.5285	$131.53	$131.55	$131.50
Purchase #6	$31.86	13.164%	$36.0541	$36.05	$36.05	$36.10
Purchase #7	$22.86	3.409%	$23.6393	$23.64	$23.65	$23.60
7 purchase totals =	$485.33		$535.0089	$535.00	$535.05	$535.00