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	$153.54	7.416%	$164.9265	$164.93	$164.95	$164.90
Purchase #2	$201.53	11.842%	$225.3952	$225.40	$225.40	$225.40
Purchase #3	$92.81	12.173%	$104.1078	$104.11	$104.10	$104.10
Purchase #4	$164.77	12.809%	$185.8754	$185.88	$185.90	$185.90
Purchase #5	$149.39	3.427%	$154.5096	$154.51	$154.50	$154.50
Purchase #6	$10.46	11.529%	$11.6659	$11.67	$11.65	$11.70
Purchase #7	$144.73	11.256%	$161.0208	$161.02	$161.00	$161.00
7 purchase totals =	$917.23		$1,007.5012	$1,007.52	$1,007.50	$1,007.50