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	$183.77	8.140%	$198.7289	$198.73	$198.75	$198.70
Purchase #2	$131.79	13.714%	$149.8637	$149.86	$149.85	$149.90
Purchase #3	$141.69	9.698%	$155.4311	$155.43	$155.45	$155.40
Purchase #4	$174.85	6.263%	$185.8009	$185.80	$185.80	$185.80
Purchase #5	$73.80	13.584%	$83.825	$83.83	$83.85	$83.80
Purchase #6	$137.48	13.454%	$155.9766	$155.98	$156.00	$156.00
Purchase #7	$121.51	8.361%	$131.6695	$131.67	$131.65	$131.70
7 purchase totals =	$964.89		$1,061.2957	$1,061.30	$1,061.35	$1,061.30