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	$171.47	12.171%	$192.3396	$192.34	$192.35	$192.30
Purchase #2	$132.27	9.870%	$145.325	$145.33	$145.35	$145.30
Purchase #3	$50.63	4.174%	$52.7433	$52.74	$52.75	$52.70
Purchase #4	$104.48	3.628%	$108.2705	$108.27	$108.25	$108.30
Purchase #5	$205.28	8.429%	$222.5831	$222.58	$222.60	$222.60
Purchase #6	$137.83	8.259%	$149.2134	$149.21	$149.20	$149.20
Purchase #7	$244.90	12.342%	$275.1256	$275.13	$275.15	$275.10
7 purchase totals =	$1,046.86		$1,145.6005	$1,145.60	$1,145.65	$1,145.50