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	$190.82	7.638%	$205.3948	$205.39	$205.40	$205.40
Purchase #2	$110.55	12.409%	$124.2681	$124.27	$124.25	$124.30
Purchase #3	$213.79	11.140%	$237.6062	$237.61	$237.60	$237.60
Purchase #4	$201.50	5.597%	$212.778	$212.78	$212.80	$212.80
Purchase #5	$130.34	13.522%	$147.9646	$147.96	$147.95	$148.00
Purchase #6	$111.79	4.512%	$116.834	$116.83	$116.85	$116.80
Purchase #7	$53.51	10.821%	$59.3003	$59.30	$59.30	$59.30
7 purchase totals =	$1,012.30		$1,104.1460	$1,104.14	$1,104.15	$1,104.20