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	$88.78	9.676%	$97.3704	$97.37	$97.35	$97.40
Purchase #2	$190.70	13.713%	$216.8507	$216.85	$216.85	$216.90
Purchase #3	$143.79	3.136%	$148.2993	$148.30	$148.30	$148.30
Purchase #4	$152.83	12.184%	$171.4508	$171.45	$171.45	$171.50
Purchase #5	$137.44	6.776%	$146.7529	$146.75	$146.75	$146.80
Purchase #6	$59.39	11.596%	$66.2769	$66.28	$66.30	$66.30
Purchase #7	$205.52	11.809%	$229.7899	$229.79	$229.80	$229.80
7 purchase totals =	$978.45		$1,076.7909	$1,076.79	$1,076.80	$1,077.00