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	$216.86	11.689%	$242.2088	$242.21	$242.20	$242.20
Purchase #2	$245.79	13.727%	$279.5296	$279.53	$279.55	$279.50
Purchase #3	$63.46	13.367%	$71.9427	$71.94	$71.95	$71.90
Purchase #4	$17.39	10.325%	$19.1855	$19.19	$19.20	$19.20
Purchase #5	$215.65	3.837%	$223.9245	$223.92	$223.90	$223.90
Purchase #6	$184.87	7.570%	$198.8647	$198.86	$198.85	$198.90
Purchase #7	$160.33	5.340%	$168.8916	$168.89	$168.90	$168.90
7 purchase totals =	$1,104.35		$1,204.5474	$1,204.54	$1,204.55	$1,204.50