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	$74.54	11.823%	$83.3529	$83.35	$83.35	$83.40
Purchase #2	$244.33	10.446%	$269.8527	$269.85	$269.85	$269.90
Purchase #3	$43.39	13.595%	$49.2889	$49.29	$49.30	$49.30
Purchase #4	$65.66	9.250%	$71.7336	$71.73	$71.75	$71.70
Purchase #5	$118.73	5.166%	$124.8636	$124.86	$124.85	$124.90
Purchase #6	$76.66	6.818%	$81.8867	$81.89	$81.90	$81.90
Purchase #7	$11.91	11.639%	$13.2962	$13.30	$13.30	$13.30
7 purchase totals =	$635.22		$694.2746	$694.27	$694.30	$694.40