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	$71.85	3.261%	$74.193	$74.19	$74.20	$74.20
Purchase #2	$52.33	13.678%	$59.4877	$59.49	$59.50	$59.50
Purchase #3	$232.77	5.624%	$245.861	$245.86	$245.85	$245.90
Purchase #4	$105.91	12.156%	$118.7844	$118.78	$118.80	$118.80
Purchase #5	$24.64	13.805%	$28.0416	$28.04	$28.05	$28.00
Purchase #6	$170.88	11.415%	$190.386	$190.39	$190.40	$190.40
Purchase #7	$215.66	10.438%	$238.1706	$238.17	$238.15	$238.20
7 purchase totals =	$874.04		$954.9243	$954.92	$954.95	$955.00