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	$55.89	12.296%	$62.7622	$62.76	$62.75	$62.80
Purchase #2	$209.89	5.568%	$221.5767	$221.58	$221.60	$221.60
Purchase #3	$7.69	11.472%	$8.5722	$8.57	$8.55	$8.60
Purchase #4	$13.92	6.119%	$14.7718	$14.77	$14.75	$14.80
Purchase #5	$105.35	7.131%	$112.8625	$112.86	$112.85	$112.90
Purchase #6	$76.44	13.243%	$86.5629	$86.56	$86.55	$86.60
Purchase #7	$236.89	3.613%	$245.4488	$245.45	$245.45	$245.40
7 purchase totals =	$706.07		$752.5571	$752.55	$752.50	$752.70