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	$140.62	9.706%	$154.2686	$154.27	$154.25	$154.30
Purchase #2	$230.56	5.792%	$243.914	$243.91	$243.90	$243.90
Purchase #3	$135.85	5.785%	$143.7089	$143.71	$143.70	$143.70
Purchase #4	$220.95	11.549%	$246.4675	$246.47	$246.45	$246.50
Purchase #5	$101.91	9.237%	$111.3234	$111.32	$111.30	$111.30
Purchase #6	$216.69	9.494%	$237.2625	$237.26	$237.25	$237.30
Purchase #7	$80.98	5.380%	$85.3367	$85.34	$85.35	$85.30
7 purchase totals =	$1,127.56		$1,222.2816	$1,222.28	$1,222.20	$1,222.30