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	$150.45	12.647%	$169.4774	$169.48	$169.50	$169.50
Purchase #2	$213.54	5.864%	$226.062	$226.06	$226.05	$226.10
Purchase #3	$159.47	4.801%	$167.1262	$167.13	$167.15	$167.10
Purchase #4	$113.32	3.625%	$117.4279	$117.43	$117.45	$117.40
Purchase #5	$73.84	12.718%	$83.231	$83.23	$83.25	$83.20
Purchase #6	$237.94	11.740%	$265.8742	$265.87	$265.85	$265.90
Purchase #7	$91.34	10.406%	$100.8448	$100.84	$100.85	$100.80
7 purchase totals =	$1,039.90		$1,130.0435	$1,130.04	$1,130.10	$1,130.00