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	$225.84	5.306%	$237.8231	$237.82	$237.80	$237.80
Purchase #2	$36.66	7.725%	$39.492	$39.49	$39.50	$39.50
Purchase #3	$63.99	11.755%	$71.512	$71.51	$71.50	$71.50
Purchase #4	$131.61	8.177%	$142.3717	$142.37	$142.35	$142.40
Purchase #5	$43.61	3.732%	$45.2375	$45.24	$45.25	$45.20
Purchase #6	$48.77	10.747%	$54.0113	$54.01	$54.00	$54.00
Purchase #7	$135.97	6.267%	$144.4912	$144.49	$144.50	$144.50
7 purchase totals =	$686.45		$734.9388	$734.93	$734.90	$734.90