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	$234.49	8.686%	$254.8578	$254.86	$254.85	$254.90
Purchase #2	$60.70	8.638%	$65.9433	$65.94	$65.95	$65.90
Purchase #3	$204.51	11.418%	$227.861	$227.86	$227.85	$227.90
Purchase #4	$43.33	7.490%	$46.5754	$46.58	$46.60	$46.60
Purchase #5	$185.78	13.124%	$210.1618	$210.16	$210.15	$210.20
Purchase #6	$127.96	7.760%	$137.8897	$137.89	$137.90	$137.90
Purchase #7	$216.90	5.678%	$229.2156	$229.22	$229.20	$229.20
7 purchase totals =	$1,073.67		$1,172.5046	$1,172.51	$1,172.50	$1,172.60