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	$145.75	6.594%	$155.3608	$155.36	$155.35	$155.40
Purchase #2	$26.57	7.588%	$28.5861	$28.59	$28.60	$28.60
Purchase #3	$209.67	10.250%	$231.1612	$231.16	$231.15	$231.20
Purchase #4	$123.43	12.632%	$139.0217	$139.02	$139.00	$139.00
Purchase #5	$209.47	6.290%	$222.6457	$222.65	$222.65	$222.60
Purchase #6	$164.64	6.813%	$175.8569	$175.86	$175.85	$175.90
Purchase #7	$81.76	10.243%	$90.1347	$90.13	$90.15	$90.10
7 purchase totals =	$961.29		$1,042.7671	$1,042.77	$1,042.75	$1,042.80