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	$135.65	4.218%	$141.3717	$141.37	$141.35	$141.40
Purchase #2	$130.33	5.295%	$137.231	$137.23	$137.25	$137.20
Purchase #3	$181.34	10.625%	$200.6074	$200.61	$200.60	$200.60
Purchase #4	$155.58	4.253%	$162.1968	$162.20	$162.20	$162.20
Purchase #5	$199.83	11.312%	$222.4348	$222.43	$222.45	$222.40
Purchase #6	$82.29	12.176%	$92.3096	$92.31	$92.30	$92.30
Purchase #7	$37.26	8.685%	$40.496	$40.50	$40.50	$40.50
7 purchase totals =	$922.28		$996.6473	$996.65	$996.65	$996.60