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	$136.28	4.517%	$142.4358	$142.44	$142.45	$142.40
Purchase #2	$151.98	4.143%	$158.2765	$158.28	$158.30	$158.30
Purchase #3	$100.82	8.638%	$109.5288	$109.53	$109.55	$109.50
Purchase #4	$155.69	3.648%	$161.3696	$161.37	$161.35	$161.40
Purchase #5	$161.81	13.359%	$183.4262	$183.43	$183.45	$183.40
Purchase #6	$85.69	11.802%	$95.8031	$95.80	$95.80	$95.80
Purchase #7	$216.82	12.599%	$244.1372	$244.14	$244.15	$244.10
7 purchase totals =	$1,009.09		$1,094.9772	$1,094.99	$1,095.05	$1,094.90