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	$92.88	7.687%	$100.0197	$100.02	$100.00	$100.00
Purchase #2	$22.76	11.217%	$25.313	$25.31	$25.30	$25.30
Purchase #3	$113.44	12.352%	$127.4521	$127.45	$127.45	$127.50
Purchase #4	$155.37	8.484%	$168.5516	$168.55	$168.55	$168.60
Purchase #5	$71.96	7.644%	$77.4606	$77.46	$77.45	$77.50
Purchase #6	$190.27	9.858%	$209.0268	$209.03	$209.05	$209.00
Purchase #7	$90.69	9.411%	$99.2248	$99.22	$99.20	$99.20
7 purchase totals =	$737.37		$807.0486	$807.04	$807.00	$807.10