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	$230.49	6.828%	$246.2279	$246.23	$246.25	$246.20
Purchase #2	$65.90	8.511%	$71.5087	$71.51	$71.50	$71.50
Purchase #3	$226.45	9.794%	$248.6285	$248.63	$248.65	$248.60
Purchase #4	$56.74	13.258%	$64.2626	$64.26	$64.25	$64.30
Purchase #5	$72.98	6.460%	$77.6945	$77.69	$77.70	$77.70
Purchase #6	$222.50	12.560%	$250.446	$250.45	$250.45	$250.40
Purchase #7	$56.69	8.518%	$61.5189	$61.52	$61.50	$61.50
7 purchase totals =	$931.75		$1,020.2871	$1,020.29	$1,020.30	$1,020.20