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	$165.94	4.154%	$172.8331	$172.83	$172.85	$172.80
Purchase #2	$213.39	11.630%	$238.2073	$238.21	$238.20	$238.20
Purchase #3	$22.40	12.237%	$25.1411	$25.14	$25.15	$25.10
Purchase #4	$182.56	9.294%	$199.5271	$199.53	$199.55	$199.50
Purchase #5	$58.58	5.293%	$61.6806	$61.68	$61.70	$61.70
Purchase #6	$209.31	4.585%	$218.9069	$218.91	$218.90	$218.90
Purchase #7	$59.64	13.421%	$67.6443	$67.64	$67.65	$67.60
7 purchase totals =	$911.82		$983.9404	$983.94	$984.00	$983.80