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	$92.78	3.345%	$95.8835	$95.88	$95.90	$95.90
Purchase #2	$61.32	4.537%	$64.1021	$64.10	$64.10	$64.10
Purchase #3	$144.36	5.503%	$152.3041	$152.30	$152.30	$152.30
Purchase #4	$221.29	10.590%	$244.7246	$244.72	$244.70	$244.70
Purchase #5	$120.83	7.764%	$130.2112	$130.21	$130.20	$130.20
Purchase #6	$189.75	4.134%	$197.5943	$197.59	$197.60	$197.60
Purchase #7	$69.48	13.454%	$78.8278	$78.83	$78.85	$78.80
7 purchase totals =	$899.81		$963.6476	$963.63	$963.65	$963.60