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	$214.54	8.762%	$233.338	$233.34	$233.35	$233.30
Purchase #2	$211.42	11.333%	$235.3802	$235.38	$235.40	$235.40
Purchase #3	$243.61	12.543%	$274.166	$274.17	$274.15	$274.20
Purchase #4	$155.36	10.851%	$172.2181	$172.22	$172.20	$172.20
Purchase #5	$79.54	13.733%	$90.4632	$90.46	$90.45	$90.50
Purchase #6	$230.38	9.144%	$251.4459	$251.45	$251.45	$251.40
Purchase #7	$115.64	4.484%	$120.8253	$120.83	$120.85	$120.80
7 purchase totals =	$1,250.49		$1,377.8367	$1,377.85	$1,377.85	$1,377.80