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	$211.62	4.789%	$221.7545	$221.75	$221.75	$221.80
Purchase #2	$242.41	10.665%	$268.263	$268.26	$268.25	$268.30
Purchase #3	$189.82	9.824%	$208.4679	$208.47	$208.45	$208.50
Purchase #4	$236.81	8.428%	$256.7683	$256.77	$256.75	$256.80
Purchase #5	$59.73	10.334%	$65.9025	$65.90	$65.90	$65.90
Purchase #6	$224.70	11.594%	$250.7517	$250.75	$250.75	$250.80
Purchase #7	$56.48	5.647%	$59.6694	$59.67	$59.65	$59.70
7 purchase totals =	$1,221.57		$1,331.5773	$1,331.57	$1,331.50	$1,331.80