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	$127.41	5.122%	$133.9359	$133.94	$133.95	$133.90
Purchase #2	$130.79	8.142%	$141.4389	$141.44	$141.45	$141.40
Purchase #3	$40.92	3.515%	$42.3583	$42.36	$42.35	$42.40
Purchase #4	$80.36	12.587%	$90.4749	$90.47	$90.45	$90.50
Purchase #5	$244.87	3.848%	$254.2926	$254.29	$254.30	$254.30
Purchase #6	$104.31	11.554%	$116.362	$116.36	$116.35	$116.40
Purchase #7	$248.38	4.629%	$259.8775	$259.88	$259.90	$259.90
7 purchase totals =	$977.04		$1,038.7401	$1,038.74	$1,038.75	$1,038.80