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	$215.77	3.587%	$223.5097	$223.51	$223.50	$223.50
Purchase #2	$162.45	10.537%	$179.5674	$179.57	$179.55	$179.60
Purchase #3	$140.90	13.170%	$159.4565	$159.46	$159.45	$159.50
Purchase #4	$55.74	7.633%	$59.9946	$59.99	$60.00	$60.00
Purchase #5	$124.58	11.534%	$138.9491	$138.95	$138.95	$138.90
Purchase #6	$148.30	9.361%	$162.1824	$162.18	$162.20	$162.20
Purchase #7	$144.77	5.525%	$152.7685	$152.77	$152.75	$152.80
7 purchase totals =	$992.51		$1,076.4282	$1,076.43	$1,076.40	$1,076.50