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	$128.84	9.232%	$140.7345	$140.73	$140.75	$140.70
Purchase #2	$172.75	6.148%	$183.3707	$183.37	$183.35	$183.40
Purchase #3	$75.62	3.639%	$78.3718	$78.37	$78.35	$78.40
Purchase #4	$144.72	9.707%	$158.768	$158.77	$158.75	$158.80
Purchase #5	$72.29	6.472%	$76.9686	$76.97	$76.95	$77.00
Purchase #6	$161.42	5.264%	$169.9171	$169.92	$169.90	$169.90
Purchase #7	$54.82	8.193%	$59.3114	$59.31	$59.30	$59.30
7 purchase totals =	$810.46		$867.4421	$867.44	$867.35	$867.50