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	$142.48	4.122%	$148.353	$148.35	$148.35	$148.40
Purchase #2	$221.91	9.471%	$242.9271	$242.93	$242.95	$242.90
Purchase #3	$172.34	10.743%	$190.8545	$190.85	$190.85	$190.90
Purchase #4	$187.98	11.589%	$209.765	$209.77	$209.75	$209.80
Purchase #5	$60.49	13.184%	$68.465	$68.47	$68.45	$68.50
Purchase #6	$7.35	7.773%	$7.9213	$7.92	$7.90	$7.90
Purchase #7	$78.78	9.620%	$86.3586	$86.36	$86.35	$86.40
7 purchase totals =	$871.33		$954.6445	$954.65	$954.60	$954.80