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	$28.58	11.419%	$31.8436	$31.84	$31.85	$31.80
Purchase #2	$55.37	3.399%	$57.252	$57.25	$57.25	$57.30
Purchase #3	$105.57	12.673%	$118.9489	$118.95	$118.95	$118.90
Purchase #4	$248.58	10.309%	$274.2061	$274.21	$274.20	$274.20
Purchase #5	$71.36	10.507%	$78.8578	$78.86	$78.85	$78.90
Purchase #6	$243.31	12.343%	$273.3418	$273.34	$273.35	$273.30
Purchase #7	$204.73	7.582%	$220.2526	$220.25	$220.25	$220.30
7 purchase totals =	$957.50		$1,054.7028	$1,054.70	$1,054.70	$1,054.70