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	$203.40	5.531%	$214.6501	$214.65	$214.65	$214.70
Purchase #2	$227.55	6.720%	$242.8414	$242.84	$242.85	$242.80
Purchase #3	$37.64	6.788%	$40.195	$40.20	$40.20	$40.20
Purchase #4	$223.49	6.666%	$238.3878	$238.39	$238.40	$238.40
Purchase #5	$92.37	12.377%	$103.8026	$103.80	$103.80	$103.80
Purchase #6	$61.84	9.496%	$67.7123	$67.71	$67.70	$67.70
Purchase #7	$94.58	6.705%	$100.9216	$100.92	$100.90	$100.90
7 purchase totals =	$940.87		$1,008.5108	$1,008.51	$1,008.50	$1,008.50