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	$216.73	4.238%	$225.915	$225.92	$225.90	$225.90
Purchase #2	$243.79	10.590%	$269.6074	$269.61	$269.60	$269.60
Purchase #3	$118.83	6.328%	$126.3496	$126.35	$126.35	$126.30
Purchase #4	$234.86	12.424%	$264.039	$264.04	$264.05	$264.00
Purchase #5	$245.27	10.332%	$270.6113	$270.61	$270.60	$270.60
Purchase #6	$174.62	3.738%	$181.1473	$181.15	$181.15	$181.10
Purchase #7	$51.32	8.733%	$55.8018	$55.80	$55.80	$55.80
7 purchase totals =	$1,285.42		$1,393.4714	$1,393.48	$1,393.45	$1,393.30