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	$104.45	8.277%	$113.0953	$113.10	$113.10	$113.10
Purchase #2	$72.50	8.220%	$78.4595	$78.46	$78.45	$78.50
Purchase #3	$136.83	11.338%	$152.3438	$152.34	$152.35	$152.30
Purchase #4	$190.49	10.161%	$209.8457	$209.85	$209.85	$209.80
Purchase #5	$190.36	8.136%	$205.8477	$205.85	$205.85	$205.80
Purchase #6	$247.77	9.380%	$271.0108	$271.01	$271.00	$271.00
Purchase #7	$225.54	4.605%	$235.9261	$235.93	$235.95	$235.90
7 purchase totals =	$1,167.94		$1,266.5289	$1,266.54	$1,266.55	$1,266.40