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	$191.77	11.102%	$213.0603	$213.06	$213.05	$213.10
Purchase #2	$160.39	13.614%	$182.2255	$182.23	$182.25	$182.20
Purchase #3	$56.69	13.124%	$64.13	$64.13	$64.15	$64.10
Purchase #4	$132.98	8.832%	$144.7248	$144.72	$144.70	$144.70
Purchase #5	$138.80	11.405%	$154.6301	$154.63	$154.65	$154.60
Purchase #6	$153.86	7.805%	$165.8688	$165.87	$165.85	$165.90
Purchase #7	$237.76	7.579%	$255.7798	$255.78	$255.80	$255.80
7 purchase totals =	$1,072.25		$1,180.4193	$1,180.42	$1,180.45	$1,180.40