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	$166.60	13.472%	$189.0444	$189.04	$189.05	$189.00
Purchase #2	$208.27	12.385%	$234.0642	$234.06	$234.05	$234.10
Purchase #3	$22.79	6.292%	$24.2239	$24.22	$24.20	$24.20
Purchase #4	$243.45	4.853%	$255.2646	$255.26	$255.25	$255.30
Purchase #5	$205.34	8.827%	$223.4654	$223.47	$223.45	$223.50
Purchase #6	$89.41	12.774%	$100.8312	$100.83	$100.85	$100.80
Purchase #7	$222.33	6.581%	$236.9615	$236.96	$236.95	$237.00
7 purchase totals =	$1,158.19		$1,263.8552	$1,263.84	$1,263.80	$1,263.90