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	$215.54	10.700%	$238.6028	$238.60	$238.60	$238.60
Purchase #2	$88.73	8.630%	$96.3874	$96.39	$96.40	$96.40
Purchase #3	$233.51	6.142%	$247.8522	$247.85	$247.85	$247.90
Purchase #4	$16.71	11.321%	$18.6017	$18.60	$18.60	$18.60
Purchase #5	$114.84	13.294%	$130.1068	$130.11	$130.10	$130.10
Purchase #6	$238.69	8.254%	$258.3915	$258.39	$258.40	$258.40
Purchase #7	$215.82	7.770%	$232.5892	$232.59	$232.60	$232.60
7 purchase totals =	$1,123.84		$1,222.5316	$1,222.53	$1,222.55	$1,222.60