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	$86.96	7.528%	$93.5063	$93.51	$93.50	$93.50
Purchase #2	$183.45	7.251%	$196.752	$196.75	$196.75	$196.80
Purchase #3	$208.47	12.166%	$233.8325	$233.83	$233.85	$233.80
Purchase #4	$69.85	11.788%	$78.0839	$78.08	$78.10	$78.10
Purchase #5	$185.69	5.299%	$195.5297	$195.53	$195.55	$195.50
Purchase #6	$30.80	13.288%	$34.8927	$34.89	$34.90	$34.90
Purchase #7	$160.56	7.194%	$172.1107	$172.11	$172.10	$172.10
7 purchase totals =	$925.78		$1,004.7078	$1,004.70	$1,004.75	$1,004.70