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	$72.80	6.493%	$77.5269	$77.53	$77.55	$77.50
Purchase #2	$60.85	8.140%	$65.8032	$65.80	$65.80	$65.80
Purchase #3	$66.27	5.469%	$69.8943	$69.89	$69.90	$69.90
Purchase #4	$52.53	12.457%	$59.0737	$59.07	$59.05	$59.10
Purchase #5	$203.32	4.793%	$213.0651	$213.07	$213.05	$213.10
Purchase #6	$53.38	11.411%	$59.4712	$59.47	$59.45	$59.50
Purchase #7	$231.35	6.767%	$247.0055	$247.01	$247.00	$247.00
7 purchase totals =	$740.50		$791.8399	$791.84	$791.80	$791.90