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	$221.40	7.546%	$238.1068	$238.11	$238.10	$238.10
Purchase #2	$174.32	12.165%	$195.526	$195.53	$195.55	$195.50
Purchase #3	$155.81	7.379%	$167.3072	$167.31	$167.30	$167.30
Purchase #4	$204.88	13.867%	$233.2907	$233.29	$233.30	$233.30
Purchase #5	$206.48	10.502%	$228.1645	$228.16	$228.15	$228.20
Purchase #6	$34.67	12.173%	$38.8904	$38.89	$38.90	$38.90
Purchase #7	$163.80	13.502%	$185.9163	$185.92	$185.90	$185.90
7 purchase totals =	$1,161.36		$1,287.2019	$1,287.21	$1,287.20	$1,287.20