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	$41.33	8.633%	$44.898	$44.90	$44.90	$44.90
Purchase #2	$117.89	8.456%	$127.8588	$127.86	$127.85	$127.90
Purchase #3	$154.28	10.553%	$170.5612	$170.56	$170.55	$170.60
Purchase #4	$84.96	7.531%	$91.3583	$91.36	$91.35	$91.40
Purchase #5	$66.45	10.172%	$73.2093	$73.21	$73.20	$73.20
Purchase #6	$169.48	5.712%	$179.1607	$179.16	$179.15	$179.20
Purchase #7	$53.54	11.485%	$59.6891	$59.69	$59.70	$59.70
7 purchase totals =	$687.93		$746.7354	$746.74	$746.70	$746.90