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	$232.27	12.519%	$261.3479	$261.35	$261.35	$261.30
Purchase #2	$151.97	11.139%	$168.8979	$168.90	$168.90	$168.90
Purchase #3	$82.78	3.162%	$85.3975	$85.40	$85.40	$85.40
Purchase #4	$124.49	7.263%	$133.5317	$133.53	$133.55	$133.50
Purchase #5	$116.82	11.622%	$130.3968	$130.40	$130.40	$130.40
Purchase #6	$84.30	7.168%	$90.3426	$90.34	$90.35	$90.30
Purchase #7	$172.89	8.629%	$187.8087	$187.81	$187.80	$187.80
7 purchase totals =	$965.52		$1,057.7231	$1,057.73	$1,057.75	$1,057.60