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	$202.50	6.714%	$216.0959	$216.10	$216.10	$216.10
Purchase #2	$208.75	3.784%	$216.6491	$216.65	$216.65	$216.60
Purchase #3	$91.82	12.533%	$103.3278	$103.33	$103.35	$103.30
Purchase #4	$150.89	13.272%	$170.9161	$170.92	$170.90	$170.90
Purchase #5	$132.43	11.262%	$147.3443	$147.34	$147.35	$147.30
Purchase #6	$115.84	13.390%	$131.351	$131.35	$131.35	$131.40
Purchase #7	$37.57	6.469%	$40.0004	$40.00	$40.00	$40.00
7 purchase totals =	$939.80		$1,025.6846	$1,025.69	$1,025.70	$1,025.60