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	$199.90	6.785%	$213.4632	$213.46	$213.45	$213.50
Purchase #2	$96.91	12.816%	$109.33	$109.33	$109.35	$109.30
Purchase #3	$196.28	10.554%	$216.9954	$217.00	$217.00	$217.00
Purchase #4	$83.93	4.633%	$87.8185	$87.82	$87.80	$87.80
Purchase #5	$71.77	9.508%	$78.5939	$78.59	$78.60	$78.60
Purchase #6	$209.90	9.432%	$229.6978	$229.70	$229.70	$229.70
Purchase #7	$96.60	12.336%	$108.5166	$108.52	$108.50	$108.50
7 purchase totals =	$955.29		$1,044.4154	$1,044.42	$1,044.40	$1,044.40