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	$84.44	10.259%	$93.1027	$93.10	$93.10	$93.10
Purchase #2	$195.79	10.231%	$215.8213	$215.82	$215.80	$215.80
Purchase #3	$40.45	7.615%	$43.5303	$43.53	$43.55	$43.50
Purchase #4	$57.73	3.665%	$59.8458	$59.85	$59.85	$59.80
Purchase #5	$52.92	13.322%	$59.97	$59.97	$59.95	$60.00
Purchase #6	$183.87	7.124%	$196.9689	$196.97	$196.95	$197.00
Purchase #7	$200.26	11.331%	$222.9515	$222.95	$222.95	$223.00
7 purchase totals =	$815.46		$892.1905	$892.19	$892.15	$892.20