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	$198.26	11.870%	$221.7935	$221.79	$221.80	$221.80
Purchase #2	$80.39	6.152%	$85.3356	$85.34	$85.35	$85.30
Purchase #3	$140.37	5.404%	$147.9556	$147.96	$147.95	$148.00
Purchase #4	$165.91	9.370%	$181.4558	$181.46	$181.45	$181.50
Purchase #5	$45.99	5.104%	$48.3373	$48.34	$48.35	$48.30
Purchase #6	$7.29	5.834%	$7.7153	$7.72	$7.70	$7.70
Purchase #7	$237.54	8.165%	$256.9351	$256.94	$256.95	$256.90
7 purchase totals =	$875.75		$949.5282	$949.55	$949.55	$949.50