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	$32.33	13.242%	$36.6111	$36.61	$36.60	$36.60
Purchase #2	$150.95	9.714%	$165.6133	$165.61	$165.60	$165.60
Purchase #3	$167.81	4.456%	$175.2876	$175.29	$175.30	$175.30
Purchase #4	$232.61	6.279%	$247.2156	$247.22	$247.20	$247.20
Purchase #5	$33.43	4.666%	$34.9898	$34.99	$35.00	$35.00
Purchase #6	$248.79	13.316%	$281.9189	$281.92	$281.90	$281.90
Purchase #7	$141.67	6.814%	$151.3234	$151.32	$151.30	$151.30
7 purchase totals =	$1,007.59		$1,092.9597	$1,092.96	$1,092.90	$1,092.90