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	$184.62	8.726%	$200.7299	$200.73	$200.75	$200.70
Purchase #2	$148.34	13.263%	$168.0143	$168.01	$168.00	$168.00
Purchase #3	$71.66	12.205%	$80.4061	$80.41	$80.40	$80.40
Purchase #4	$107.57	5.666%	$113.6649	$113.66	$113.65	$113.70
Purchase #5	$17.87	13.485%	$20.2798	$20.28	$20.30	$20.30
Purchase #6	$66.80	8.570%	$72.5248	$72.52	$72.50	$72.50
Purchase #7	$250.36	10.581%	$276.8506	$276.85	$276.85	$276.90
7 purchase totals =	$847.22		$932.4704	$932.46	$932.45	$932.50