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	$166.82	13.156%	$188.7668	$188.77	$188.75	$188.80
Purchase #2	$139.41	9.497%	$152.6498	$152.65	$152.65	$152.60
Purchase #3	$140.99	10.389%	$155.6375	$155.64	$155.65	$155.60
Purchase #4	$133.96	13.171%	$151.6039	$151.60	$151.60	$151.60
Purchase #5	$243.82	11.468%	$271.7813	$271.78	$271.80	$271.80
Purchase #6	$166.35	12.518%	$187.1737	$187.17	$187.15	$187.20
Purchase #7	$58.78	5.235%	$61.8571	$61.86	$61.85	$61.90
7 purchase totals =	$1,050.13		$1,169.4701	$1,169.47	$1,169.45	$1,169.50