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	$77.81	5.512%	$82.0989	$82.10	$82.10	$82.10
Purchase #2	$138.25	8.594%	$150.1312	$150.13	$150.15	$150.10
Purchase #3	$9.82	11.157%	$10.9156	$10.92	$10.90	$10.90
Purchase #4	$167.91	9.467%	$183.806	$183.81	$183.80	$183.80
Purchase #5	$87.30	3.668%	$90.5022	$90.50	$90.50	$90.50
Purchase #6	$110.60	4.421%	$115.4896	$115.49	$115.50	$115.50
Purchase #7	$67.74	6.468%	$72.1214	$72.12	$72.10	$72.10
7 purchase totals =	$659.43		$705.0649	$705.07	$705.05	$705.00