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	$97.34	9.348%	$106.4393	$106.44	$106.45	$106.40
Purchase #2	$122.55	7.316%	$131.5158	$131.52	$131.50	$131.50
Purchase #3	$54.35	9.543%	$59.5366	$59.54	$59.55	$59.50
Purchase #4	$36.27	11.690%	$40.51	$40.51	$40.50	$40.50
Purchase #5	$193.90	5.102%	$203.7928	$203.79	$203.80	$203.80
Purchase #6	$99.61	10.466%	$110.0352	$110.04	$110.05	$110.00
Purchase #7	$226.44	12.192%	$254.0476	$254.05	$254.05	$254.00
7 purchase totals =	$830.46		$905.8773	$905.89	$905.90	$905.70