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	$159.65	6.304%	$169.7143	$169.71	$169.70	$169.70
Purchase #2	$231.59	7.403%	$248.7346	$248.73	$248.75	$248.70
Purchase #3	$72.41	13.551%	$82.2223	$82.22	$82.20	$82.20
Purchase #4	$48.87	9.497%	$53.5112	$53.51	$53.50	$53.50
Purchase #5	$207.41	4.252%	$216.2291	$216.23	$216.25	$216.20
Purchase #6	$220.65	8.872%	$240.2261	$240.23	$240.25	$240.20
Purchase #7	$141.82	11.568%	$158.2257	$158.23	$158.25	$158.20
7 purchase totals =	$1,082.40		$1,168.8633	$1,168.86	$1,168.90	$1,168.70