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	$119.90	6.665%	$127.8913	$127.89	$127.90	$127.90
Purchase #2	$61.57	7.660%	$66.2863	$66.29	$66.30	$66.30
Purchase #3	$151.88	9.131%	$165.7482	$165.75	$165.75	$165.70
Purchase #4	$100.72	3.814%	$104.5615	$104.56	$104.55	$104.60
Purchase #5	$241.79	6.434%	$257.3468	$257.35	$257.35	$257.30
Purchase #6	$169.56	7.446%	$182.1854	$182.19	$182.20	$182.20
Purchase #7	$58.63	10.778%	$64.9491	$64.95	$64.95	$64.90
7 purchase totals =	$904.05		$968.9686	$968.98	$969.00	$968.90