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	$137.60	7.248%	$147.5732	$147.57	$147.55	$147.60
Purchase #2	$101.30	4.446%	$105.8038	$105.80	$105.80	$105.80
Purchase #3	$84.34	13.727%	$95.9174	$95.92	$95.90	$95.90
Purchase #4	$148.93	6.402%	$158.4645	$158.46	$158.45	$158.50
Purchase #5	$118.34	4.352%	$123.4902	$123.49	$123.50	$123.50
Purchase #6	$134.86	10.382%	$148.8612	$148.86	$148.85	$148.90
Purchase #7	$31.69	8.317%	$34.3257	$34.33	$34.35	$34.30
7 purchase totals =	$757.06		$814.4360	$814.43	$814.40	$814.50