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	$165.57	8.122%	$179.0176	$179.02	$179.00	$179.00
Purchase #2	$28.64	12.772%	$32.2979	$32.30	$32.30	$32.30
Purchase #3	$88.48	7.698%	$95.2912	$95.29	$95.30	$95.30
Purchase #4	$25.38	6.530%	$27.0373	$27.04	$27.05	$27.00
Purchase #5	$145.43	13.300%	$164.7722	$164.77	$164.75	$164.80
Purchase #6	$178.78	7.305%	$191.8399	$191.84	$191.85	$191.80
Purchase #7	$159.75	7.700%	$172.0508	$172.05	$172.05	$172.10
7 purchase totals =	$792.03		$862.3069	$862.31	$862.30	$862.30