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	$194.42	5.638%	$205.3814	$205.38	$205.40	$205.40
Purchase #2	$104.50	6.419%	$111.2079	$111.21	$111.20	$111.20
Purchase #3	$22.89	6.140%	$24.2954	$24.30	$24.30	$24.30
Purchase #4	$21.40	4.597%	$22.3838	$22.38	$22.40	$22.40
Purchase #5	$139.43	13.555%	$158.3297	$158.33	$158.35	$158.30
Purchase #6	$77.53	9.693%	$85.045	$85.05	$85.05	$85.00
Purchase #7	$142.78	3.238%	$147.4032	$147.40	$147.40	$147.40
7 purchase totals =	$702.95		$754.0464	$754.05	$754.10	$754.00