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	$190.76	4.261%	$198.8883	$198.89	$198.90	$198.90
Purchase #2	$132.48	6.820%	$141.5151	$141.52	$141.50	$141.50
Purchase #3	$48.68	13.656%	$55.3277	$55.33	$55.35	$55.30
Purchase #4	$82.68	10.547%	$91.4003	$91.40	$91.40	$91.40
Purchase #5	$60.86	3.777%	$63.1587	$63.16	$63.15	$63.20
Purchase #6	$213.82	13.781%	$243.2865	$243.29	$243.30	$243.30
Purchase #7	$12.45	7.457%	$13.3784	$13.38	$13.40	$13.40
7 purchase totals =	$741.73		$806.9550	$806.97	$807.00	$807.00