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	$41.44	9.416%	$45.342	$45.34	$45.35	$45.30
Purchase #2	$109.53	8.142%	$118.4479	$118.45	$118.45	$118.40
Purchase #3	$195.44	11.614%	$218.1384	$218.14	$218.15	$218.10
Purchase #4	$19.47	4.448%	$20.336	$20.34	$20.35	$20.30
Purchase #5	$12.82	9.777%	$14.0734	$14.07	$14.05	$14.10
Purchase #6	$39.52	10.537%	$43.6842	$43.68	$43.70	$43.70
Purchase #7	$92.66	7.695%	$99.7902	$99.79	$99.80	$99.80
7 purchase totals =	$510.88		$559.8121	$559.81	$559.85	$559.70