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	$140.62	8.362%	$152.3786	$152.38	$152.40	$152.40
Purchase #2	$119.48	4.183%	$124.4778	$124.48	$124.50	$124.50
Purchase #3	$164.44	5.501%	$173.4858	$173.49	$173.50	$173.50
Purchase #4	$83.90	7.182%	$89.9257	$89.93	$89.95	$89.90
Purchase #5	$121.49	9.171%	$132.6318	$132.63	$132.65	$132.60
Purchase #6	$150.90	7.670%	$162.474	$162.47	$162.45	$162.50
Purchase #7	$177.42	12.815%	$200.1564	$200.16	$200.15	$200.20
7 purchase totals =	$958.25		$1,035.5301	$1,035.54	$1,035.60	$1,035.60