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	$200.56	6.256%	$213.107	$213.11	$213.10	$213.10
Purchase #2	$225.68	13.473%	$256.0859	$256.09	$256.10	$256.10
Purchase #3	$234.79	13.239%	$265.8738	$265.87	$265.85	$265.90
Purchase #4	$228.58	4.511%	$238.8912	$238.89	$238.90	$238.90
Purchase #5	$18.28	13.682%	$20.7811	$20.78	$20.80	$20.80
Purchase #6	$37.66	12.516%	$42.3735	$42.37	$42.35	$42.40
Purchase #7	$43.61	9.610%	$47.8009	$47.80	$47.80	$47.80
7 purchase totals =	$989.16		$1,084.9134	$1,084.91	$1,084.90	$1,085.00