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	$235.98	12.194%	$264.7554	$264.76	$264.75	$264.80
Purchase #2	$208.78	6.563%	$222.4822	$222.48	$222.50	$222.50
Purchase #3	$48.25	4.716%	$50.5255	$50.53	$50.55	$50.50
Purchase #4	$195.32	13.386%	$221.4655	$221.47	$221.45	$221.50
Purchase #5	$69.89	11.746%	$78.0993	$78.10	$78.10	$78.10
Purchase #6	$141.27	12.171%	$158.464	$158.46	$158.45	$158.50
Purchase #7	$222.66	6.470%	$237.0661	$237.07	$237.05	$237.10
7 purchase totals =	$1,122.15		$1,232.8580	$1,232.87	$1,232.85	$1,233.00