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	$45.32	10.871%	$50.2467	$50.25	$50.25	$50.20
Purchase #2	$216.81	7.152%	$232.3163	$232.32	$232.30	$232.30
Purchase #3	$33.93	12.349%	$38.12	$38.12	$38.10	$38.10
Purchase #4	$222.47	12.408%	$250.0741	$250.07	$250.05	$250.10
Purchase #5	$30.71	5.832%	$32.501	$32.50	$32.50	$32.50
Purchase #6	$189.77	10.857%	$210.3733	$210.37	$210.35	$210.40
Purchase #7	$209.85	3.760%	$217.7404	$217.74	$217.75	$217.70
7 purchase totals =	$948.86		$1,031.3718	$1,031.37	$1,031.30	$1,031.30