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	$223.25	4.638%	$233.6043	$233.60	$233.60	$233.60
Purchase #2	$31.53	5.781%	$33.3527	$33.35	$33.35	$33.40
Purchase #3	$48.27	10.760%	$53.4639	$53.46	$53.45	$53.50
Purchase #4	$22.44	9.694%	$24.6153	$24.62	$24.60	$24.60
Purchase #5	$131.32	8.718%	$142.7685	$142.77	$142.75	$142.80
Purchase #6	$58.57	6.561%	$62.4128	$62.41	$62.40	$62.40
Purchase #7	$144.42	4.343%	$150.6922	$150.69	$150.70	$150.70
7 purchase totals =	$659.80		$700.9097	$700.90	$700.85	$701.00