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	$188.72	3.290%	$194.9289	$194.93	$194.95	$194.90
Purchase #2	$172.67	10.645%	$191.0507	$191.05	$191.05	$191.10
Purchase #3	$221.77	5.457%	$233.872	$233.87	$233.85	$233.90
Purchase #4	$20.46	11.345%	$22.7812	$22.78	$22.80	$22.80
Purchase #5	$70.34	10.864%	$77.9817	$77.98	$78.00	$78.00
Purchase #6	$246.70	7.357%	$264.8497	$264.85	$264.85	$264.80
Purchase #7	$206.81	11.238%	$230.0513	$230.05	$230.05	$230.10
7 purchase totals =	$1,127.47		$1,215.5155	$1,215.51	$1,215.55	$1,215.60