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	$94.94	6.191%	$100.8177	$100.82	$100.80	$100.80
Purchase #2	$53.51	11.367%	$59.5925	$59.59	$59.60	$59.60
Purchase #3	$195.73	6.733%	$208.9085	$208.91	$208.90	$208.90
Purchase #4	$142.83	10.459%	$157.7686	$157.77	$157.75	$157.80
Purchase #5	$34.82	6.222%	$36.9865	$36.99	$37.00	$37.00
Purchase #6	$97.25	4.416%	$101.5446	$101.54	$101.55	$101.50
Purchase #7	$74.40	4.264%	$77.5724	$77.57	$77.55	$77.60
7 purchase totals =	$693.48		$743.1908	$743.19	$743.15	$743.20