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	$146.29	12.677%	$164.8352	$164.84	$164.85	$164.80
Purchase #2	$225.72	9.142%	$246.3553	$246.36	$246.35	$246.40
Purchase #3	$94.27	13.298%	$106.806	$106.81	$106.80	$106.80
Purchase #4	$65.84	13.373%	$74.6448	$74.64	$74.65	$74.60
Purchase #5	$99.54	11.860%	$111.3454	$111.35	$111.35	$111.30
Purchase #6	$103.81	11.758%	$116.016	$116.02	$116.00	$116.00
Purchase #7	$130.67	12.104%	$146.4863	$146.49	$146.50	$146.50
7 purchase totals =	$866.14		$966.4890	$966.51	$966.50	$966.40