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	$61.44	4.629%	$64.2841	$64.28	$64.30	$64.30
Purchase #2	$196.27	13.790%	$223.3356	$223.34	$223.35	$223.30
Purchase #3	$80.47	6.676%	$85.8422	$85.84	$85.85	$85.80
Purchase #4	$33.37	13.121%	$37.7485	$37.75	$37.75	$37.70
Purchase #5	$235.72	7.158%	$252.5928	$252.59	$252.60	$252.60
Purchase #6	$175.66	3.138%	$181.1722	$181.17	$181.15	$181.20
Purchase #7	$237.96	6.534%	$253.5083	$253.51	$253.50	$253.50
7 purchase totals =	$1,020.89		$1,098.4837	$1,098.48	$1,098.50	$1,098.40