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	$32.42	6.681%	$34.586	$34.59	$34.60	$34.60
Purchase #2	$95.67	13.282%	$108.3769	$108.38	$108.40	$108.40
Purchase #3	$219.32	5.765%	$231.9638	$231.96	$231.95	$232.00
Purchase #4	$49.60	10.545%	$54.8303	$54.83	$54.85	$54.80
Purchase #5	$137.82	10.804%	$152.7101	$152.71	$152.70	$152.70
Purchase #6	$63.73	12.401%	$71.6332	$71.63	$71.65	$71.60
Purchase #7	$174.83	4.595%	$182.8634	$182.86	$182.85	$182.90
7 purchase totals =	$773.39		$836.9637	$836.96	$837.00	$837.00