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	$67.94	3.523%	$70.3335	$70.33	$70.35	$70.30
Purchase #2	$19.29	3.715%	$20.0066	$20.01	$20.00	$20.00
Purchase #3	$153.68	12.227%	$172.4705	$172.47	$172.45	$172.50
Purchase #4	$209.35	11.478%	$233.3792	$233.38	$233.40	$233.40
Purchase #5	$57.67	7.804%	$62.1706	$62.17	$62.15	$62.20
Purchase #6	$189.92	13.679%	$215.8992	$215.90	$215.90	$215.90
Purchase #7	$247.78	11.512%	$276.3044	$276.30	$276.30	$276.30
7 purchase totals =	$945.63		$1,050.5640	$1,050.56	$1,050.55	$1,050.60