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	$180.57	8.785%	$196.4331	$196.43	$196.45	$196.40
Purchase #2	$200.64	9.297%	$219.2935	$219.29	$219.30	$219.30
Purchase #3	$240.44	6.740%	$256.6457	$256.65	$256.65	$256.60
Purchase #4	$84.53	4.621%	$88.4361	$88.44	$88.45	$88.40
Purchase #5	$240.41	10.321%	$265.2227	$265.22	$265.20	$265.20
Purchase #6	$61.26	13.802%	$69.7151	$69.72	$69.70	$69.70
Purchase #7	$145.98	9.210%	$159.4248	$159.42	$159.40	$159.40
7 purchase totals =	$1,153.83		$1,255.1710	$1,255.17	$1,255.15	$1,255.00