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	$74.56	10.865%	$82.6609	$82.66	$82.65	$82.70
Purchase #2	$5.95	8.739%	$6.47	$6.47	$6.45	$6.50
Purchase #3	$112.72	3.298%	$116.4375	$116.44	$116.45	$116.40
Purchase #4	$125.49	12.414%	$141.0683	$141.07	$141.05	$141.10
Purchase #5	$174.90	12.556%	$196.8604	$196.86	$196.85	$196.90
Purchase #6	$129.87	10.333%	$143.2895	$143.29	$143.30	$143.30
Purchase #7	$83.75	3.838%	$86.9643	$86.96	$86.95	$87.00
7 purchase totals =	$707.24		$773.7509	$773.75	$773.70	$773.90