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	$66.84	13.540%	$75.8901	$75.89	$75.90	$75.90
Purchase #2	$192.76	9.521%	$211.1127	$211.11	$211.10	$211.10
Purchase #3	$217.76	12.305%	$244.5554	$244.56	$244.55	$244.60
Purchase #4	$224.37	4.566%	$234.6147	$234.61	$234.60	$234.60
Purchase #5	$173.72	13.265%	$196.764	$196.76	$196.75	$196.80
Purchase #6	$57.31	3.337%	$59.2224	$59.22	$59.20	$59.20
Purchase #7	$131.88	5.516%	$139.1545	$139.15	$139.15	$139.20
7 purchase totals =	$1,064.64		$1,161.3138	$1,161.30	$1,161.25	$1,161.40