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	$44.58	4.151%	$46.4305	$46.43	$46.45	$46.40
Purchase #2	$72.49	11.239%	$80.6372	$80.64	$80.65	$80.60
Purchase #3	$41.74	4.208%	$43.4964	$43.50	$43.50	$43.50
Purchase #4	$124.84	4.838%	$130.8798	$130.88	$130.90	$130.90
Purchase #5	$189.87	10.285%	$209.3981	$209.40	$209.40	$209.40
Purchase #6	$41.30	3.143%	$42.5981	$42.60	$42.60	$42.60
Purchase #7	$67.91	7.378%	$72.9204	$72.92	$72.90	$72.90
7 purchase totals =	$582.73		$626.3605	$626.37	$626.40	$626.30