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	$233.90	8.223%	$253.1336	$253.13	$253.15	$253.10
Purchase #2	$64.96	4.139%	$67.6487	$67.65	$67.65	$67.60
Purchase #3	$139.82	9.149%	$152.6121	$152.61	$152.60	$152.60
Purchase #4	$250.60	10.309%	$276.4344	$276.43	$276.45	$276.40
Purchase #5	$144.69	4.655%	$151.4253	$151.43	$151.45	$151.40
Purchase #6	$240.30	10.590%	$265.7478	$265.75	$265.75	$265.70
Purchase #7	$250.98	8.283%	$271.7687	$271.77	$271.75	$271.80
7 purchase totals =	$1,325.25		$1,438.7706	$1,438.77	$1,438.80	$1,438.60