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	$145.46	3.517%	$150.5758	$150.58	$150.60	$150.60
Purchase #2	$55.46	11.132%	$61.6338	$61.63	$61.65	$61.60
Purchase #3	$147.49	8.355%	$159.8128	$159.81	$159.80	$159.80
Purchase #4	$81.79	13.190%	$92.5781	$92.58	$92.60	$92.60
Purchase #5	$191.66	7.166%	$205.3944	$205.39	$205.40	$205.40
Purchase #6	$145.86	13.570%	$165.6532	$165.65	$165.65	$165.70
Purchase #7	$223.89	13.616%	$254.3749	$254.37	$254.35	$254.40
7 purchase totals =	$991.61		$1,090.0230	$1,090.01	$1,090.05	$1,090.10