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	$33.61	3.871%	$34.911	$34.91	$34.90	$34.90
Purchase #2	$250.48	13.229%	$283.616	$283.62	$283.60	$283.60
Purchase #3	$182.79	4.681%	$191.3464	$191.35	$191.35	$191.30
Purchase #4	$112.49	13.448%	$127.6177	$127.62	$127.60	$127.60
Purchase #5	$9.42	4.684%	$9.8612	$9.86	$9.85	$9.90
Purchase #6	$207.27	7.248%	$222.2929	$222.29	$222.30	$222.30
Purchase #7	$151.59	10.504%	$167.513	$167.51	$167.50	$167.50
7 purchase totals =	$947.65		$1,037.1582	$1,037.16	$1,037.10	$1,037.10