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	$174.33	13.489%	$197.8454	$197.85	$197.85	$197.80
Purchase #2	$148.84	3.626%	$154.2369	$154.24	$154.25	$154.20
Purchase #3	$31.47	7.683%	$33.8878	$33.89	$33.90	$33.90
Purchase #4	$129.92	12.762%	$146.5004	$146.50	$146.50	$146.50
Purchase #5	$80.25	11.133%	$89.1842	$89.18	$89.20	$89.20
Purchase #6	$172.80	10.874%	$191.5903	$191.59	$191.60	$191.60
Purchase #7	$20.70	4.746%	$21.6824	$21.68	$21.70	$21.70
7 purchase totals =	$758.31		$834.9274	$834.93	$835.00	$834.90