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	$234.85	11.192%	$261.1344	$261.13	$261.15	$261.10
Purchase #2	$64.32	12.442%	$72.3227	$72.32	$72.30	$72.30
Purchase #3	$158.60	10.766%	$175.6749	$175.67	$175.65	$175.70
Purchase #4	$111.46	4.635%	$116.6262	$116.63	$116.65	$116.60
Purchase #5	$150.72	6.596%	$160.6615	$160.66	$160.65	$160.70
Purchase #6	$170.55	7.465%	$183.2816	$183.28	$183.30	$183.30
Purchase #7	$88.38	6.583%	$94.1981	$94.20	$94.20	$94.20
7 purchase totals =	$978.88		$1,063.8994	$1,063.89	$1,063.90	$1,063.90