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	$211.72	5.294%	$222.9285	$222.93	$222.95	$222.90
Purchase #2	$80.52	12.511%	$90.5939	$90.59	$90.60	$90.60
Purchase #3	$111.57	11.496%	$124.3961	$124.40	$124.40	$124.40
Purchase #4	$248.90	3.862%	$258.5125	$258.51	$258.50	$258.50
Purchase #5	$204.50	10.396%	$225.7598	$225.76	$225.75	$225.80
Purchase #6	$209.82	4.762%	$219.8116	$219.81	$219.80	$219.80
Purchase #7	$64.52	4.166%	$67.2079	$67.21	$67.20	$67.20
7 purchase totals =	$1,131.55		$1,209.2103	$1,209.21	$1,209.20	$1,209.20