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	$52.35	6.617%	$55.814	$55.81	$55.80	$55.80
Purchase #2	$137.94	10.160%	$151.9547	$151.95	$151.95	$152.00
Purchase #3	$195.76	11.343%	$217.9651	$217.97	$217.95	$218.00
Purchase #4	$240.63	8.677%	$261.5095	$261.51	$261.50	$261.50
Purchase #5	$60.87	10.699%	$67.3825	$67.38	$67.40	$67.40
Purchase #6	$30.92	4.460%	$32.299	$32.30	$32.30	$32.30
Purchase #7	$70.37	11.414%	$78.402	$78.40	$78.40	$78.40
7 purchase totals =	$788.84		$865.3268	$865.32	$865.30	$865.40