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	$41.82	9.844%	$45.9368	$45.94	$45.95	$45.90
Purchase #2	$99.42	6.235%	$105.6188	$105.62	$105.60	$105.60
Purchase #3	$6.35	10.238%	$7.0001	$7.00	$7.00	$7.00
Purchase #4	$73.63	6.384%	$78.3305	$78.33	$78.35	$78.30
Purchase #5	$44.32	3.188%	$45.7329	$45.73	$45.75	$45.70
Purchase #6	$118.34	8.728%	$128.6687	$128.67	$128.65	$128.70
Purchase #7	$30.82	8.664%	$33.4902	$33.49	$33.50	$33.50
7 purchase totals =	$414.70		$444.7780	$444.78	$444.80	$444.70