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	$93.60	10.673%	$103.5899	$103.59	$103.60	$103.60
Purchase #2	$87.37	8.217%	$94.5492	$94.55	$94.55	$94.50
Purchase #3	$8.26	7.524%	$8.8815	$8.88	$8.90	$8.90
Purchase #4	$135.84	11.315%	$151.2103	$151.21	$151.20	$151.20
Purchase #5	$194.33	5.579%	$205.1717	$205.17	$205.15	$205.20
Purchase #6	$53.89	10.375%	$59.4811	$59.48	$59.50	$59.50
Purchase #7	$106.87	6.234%	$113.5323	$113.53	$113.55	$113.50
7 purchase totals =	$680.16		$736.4160	$736.41	$736.45	$736.40