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	$60.63	6.479%	$64.5582	$64.56	$64.55	$64.60
Purchase #2	$144.45	3.562%	$149.5953	$149.60	$149.60	$149.60
Purchase #3	$146.89	3.154%	$151.5229	$151.52	$151.50	$151.50
Purchase #4	$130.64	12.830%	$147.4011	$147.40	$147.40	$147.40
Purchase #5	$48.48	4.192%	$50.5123	$50.51	$50.50	$50.50
Purchase #6	$36.71	6.511%	$39.1002	$39.10	$39.10	$39.10
Purchase #7	$142.52	9.302%	$155.7772	$155.78	$155.80	$155.80
7 purchase totals =	$710.32		$758.4672	$758.47	$758.45	$758.50