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	$72.35	13.517%	$82.1295	$82.13	$82.15	$82.10
Purchase #2	$89.82	12.500%	$101.0475	$101.05	$101.05	$101.00
Purchase #3	$164.67	12.215%	$184.7844	$184.78	$184.80	$184.80
Purchase #4	$73.93	3.563%	$76.5641	$76.56	$76.55	$76.60
Purchase #5	$125.87	4.180%	$131.1314	$131.13	$131.15	$131.10
Purchase #6	$92.73	11.698%	$103.5776	$103.58	$103.60	$103.60
Purchase #7	$73.35	6.616%	$78.2028	$78.20	$78.20	$78.20
7 purchase totals =	$692.72		$757.4373	$757.43	$757.50	$757.40