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	$237.45	7.297%	$254.7767	$254.78	$254.80	$254.80
Purchase #2	$88.31	10.364%	$97.4624	$97.46	$97.45	$97.50
Purchase #3	$196.86	11.224%	$218.9556	$218.96	$218.95	$219.00
Purchase #4	$199.92	9.559%	$219.0304	$219.03	$219.05	$219.00
Purchase #5	$114.71	7.668%	$123.506	$123.51	$123.50	$123.50
Purchase #6	$235.75	10.351%	$260.1525	$260.15	$260.15	$260.20
Purchase #7	$21.77	3.503%	$22.5326	$22.53	$22.55	$22.50
7 purchase totals =	$1,094.77		$1,196.4162	$1,196.42	$1,196.45	$1,196.50