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	$197.86	10.625%	$218.8826	$218.88	$218.90	$218.90
Purchase #2	$244.67	4.506%	$255.6948	$255.69	$255.70	$255.70
Purchase #3	$247.61	6.859%	$264.5936	$264.59	$264.60	$264.60
Purchase #4	$130.75	4.786%	$137.0077	$137.01	$137.00	$137.00
Purchase #5	$158.80	10.702%	$175.7948	$175.79	$175.80	$175.80
Purchase #6	$128.54	8.791%	$139.84	$139.84	$139.85	$139.80
Purchase #7	$89.84	6.473%	$95.6553	$95.66	$95.65	$95.70
7 purchase totals =	$1,198.07		$1,287.4688	$1,287.46	$1,287.50	$1,287.50