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	$198.26	5.582%	$209.3269	$209.33	$209.35	$209.30
Purchase #2	$198.32	5.144%	$208.5216	$208.52	$208.50	$208.50
Purchase #3	$152.44	13.360%	$172.806	$172.81	$172.80	$172.80
Purchase #4	$227.70	8.596%	$247.2731	$247.27	$247.25	$247.30
Purchase #5	$124.25	3.410%	$128.4869	$128.49	$128.50	$128.50
Purchase #6	$171.59	4.868%	$179.943	$179.94	$179.95	$179.90
Purchase #7	$80.27	12.849%	$90.5839	$90.58	$90.60	$90.60
7 purchase totals =	$1,152.83		$1,236.9414	$1,236.94	$1,236.95	$1,236.90