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	$34.56	3.391%	$35.7319	$35.73	$35.75	$35.70
Purchase #2	$179.69	6.637%	$191.616	$191.62	$191.60	$191.60
Purchase #3	$45.56	11.343%	$50.7279	$50.73	$50.75	$50.70
Purchase #4	$129.67	9.367%	$141.8162	$141.82	$141.80	$141.80
Purchase #5	$168.97	6.652%	$180.2099	$180.21	$180.20	$180.20
Purchase #6	$41.55	9.499%	$45.4968	$45.50	$45.50	$45.50
Purchase #7	$225.83	13.570%	$256.4751	$256.48	$256.50	$256.50
7 purchase totals =	$825.83		$902.0738	$902.09	$902.10	$902.00