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	$40.37	9.759%	$44.3097	$44.31	$44.30	$44.30
Purchase #2	$175.91	11.556%	$196.2382	$196.24	$196.25	$196.20
Purchase #3	$100.46	6.162%	$106.6503	$106.65	$106.65	$106.70
Purchase #4	$34.79	10.534%	$38.4548	$38.45	$38.45	$38.50
Purchase #5	$210.95	10.541%	$233.1862	$233.19	$233.20	$233.20
Purchase #6	$208.77	3.192%	$215.4339	$215.43	$215.45	$215.40
Purchase #7	$242.69	12.333%	$272.621	$272.62	$272.60	$272.60
7 purchase totals =	$1,013.94		$1,106.8941	$1,106.89	$1,106.90	$1,106.90