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	$92.56	12.148%	$103.8042	$103.80	$103.80	$103.80
Purchase #2	$235.98	7.605%	$253.9263	$253.93	$253.95	$253.90
Purchase #3	$175.59	12.141%	$196.9084	$196.91	$196.90	$196.90
Purchase #4	$57.96	10.760%	$64.1965	$64.20	$64.20	$64.20
Purchase #5	$247.59	13.476%	$280.9552	$280.96	$280.95	$281.00
Purchase #6	$123.26	13.361%	$139.7288	$139.73	$139.75	$139.70
Purchase #7	$12.82	12.324%	$14.3999	$14.40	$14.40	$14.40
7 purchase totals =	$945.76		$1,053.9193	$1,053.93	$1,053.95	$1,053.90