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	$220.84	13.410%	$250.4546	$250.45	$250.45	$250.50
Purchase #2	$212.40	6.367%	$225.9235	$225.92	$225.90	$225.90
Purchase #3	$58.28	12.388%	$65.4997	$65.50	$65.50	$65.50
Purchase #4	$24.34	13.870%	$27.716	$27.72	$27.70	$27.70
Purchase #5	$55.28	7.863%	$59.6267	$59.63	$59.65	$59.60
Purchase #6	$205.66	3.816%	$213.508	$213.51	$213.50	$213.50
Purchase #7	$30.75	6.716%	$32.8152	$32.82	$32.80	$32.80
7 purchase totals =	$807.55		$875.5437	$875.55	$875.50	$875.50