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	$153.90	7.116%	$164.8515	$164.85	$164.85	$164.90
Purchase #2	$57.48	11.393%	$64.0287	$64.03	$64.05	$64.00
Purchase #3	$138.57	10.350%	$152.912	$152.91	$152.90	$152.90
Purchase #4	$161.60	9.306%	$176.6385	$176.64	$176.65	$176.60
Purchase #5	$179.64	9.588%	$196.8639	$196.86	$196.85	$196.90
Purchase #6	$138.68	7.147%	$148.5915	$148.59	$148.60	$148.60
Purchase #7	$226.51	11.795%	$253.2269	$253.23	$253.25	$253.20
7 purchase totals =	$1,056.38		$1,157.1130	$1,157.11	$1,157.15	$1,157.10