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	$30.72	10.131%	$33.8322	$33.83	$33.85	$33.80
Purchase #2	$208.96	11.810%	$233.6382	$233.64	$233.65	$233.60
Purchase #3	$250.32	9.325%	$273.6623	$273.66	$273.65	$273.70
Purchase #4	$174.54	11.824%	$195.1776	$195.18	$195.20	$195.20
Purchase #5	$11.87	11.842%	$13.2756	$13.28	$13.30	$13.30
Purchase #6	$198.81	7.347%	$213.4166	$213.42	$213.40	$213.40
Purchase #7	$93.76	6.494%	$99.8488	$99.85	$99.85	$99.80
7 purchase totals =	$968.98		$1,062.8513	$1,062.86	$1,062.90	$1,062.80