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	$201.77	12.160%	$226.3052	$226.31	$226.30	$226.30
Purchase #2	$85.37	8.253%	$92.4156	$92.42	$92.40	$92.40
Purchase #3	$63.37	12.625%	$71.3705	$71.37	$71.35	$71.40
Purchase #4	$139.85	13.273%	$158.4123	$158.41	$158.40	$158.40
Purchase #5	$212.70	5.144%	$223.6413	$223.64	$223.65	$223.60
Purchase #6	$180.55	5.731%	$190.8973	$190.90	$190.90	$190.90
Purchase #7	$137.98	12.226%	$154.8494	$154.85	$154.85	$154.80
7 purchase totals =	$1,021.59		$1,117.8916	$1,117.90	$1,117.85	$1,117.80