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	$85.50	5.135%	$89.8904	$89.89	$89.90	$89.90
Purchase #2	$244.60	3.226%	$252.4908	$252.49	$252.50	$252.50
Purchase #3	$50.59	13.682%	$57.5117	$57.51	$57.50	$57.50
Purchase #4	$217.62	9.150%	$237.5322	$237.53	$237.55	$237.50
Purchase #5	$30.85	7.519%	$33.1696	$33.17	$33.15	$33.20
Purchase #6	$154.32	5.200%	$162.3446	$162.34	$162.35	$162.30
Purchase #7	$162.98	11.716%	$182.0747	$182.07	$182.05	$182.10
7 purchase totals =	$946.46		$1,015.0140	$1,015.00	$1,015.00	$1,015.00