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	$169.39	12.720%	$190.9364	$190.94	$190.95	$190.90
Purchase #2	$78.46	6.348%	$83.4406	$83.44	$83.45	$83.40
Purchase #3	$106.38	11.309%	$118.4105	$118.41	$118.40	$118.40
Purchase #4	$213.75	4.793%	$223.995	$224.00	$224.00	$224.00
Purchase #5	$199.40	5.657%	$210.6801	$210.68	$210.70	$210.70
Purchase #6	$90.56	11.368%	$100.8549	$100.85	$100.85	$100.90
Purchase #7	$42.49	7.635%	$45.7341	$45.73	$45.75	$45.70
7 purchase totals =	$900.43		$974.0516	$974.05	$974.10	$974.00