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	$40.50	4.327%	$42.2524	$42.25	$42.25	$42.30
Purchase #2	$61.55	9.116%	$67.1609	$67.16	$67.15	$67.20
Purchase #3	$13.48	3.655%	$13.9727	$13.97	$13.95	$14.00
Purchase #4	$95.48	8.685%	$103.7724	$103.77	$103.75	$103.80
Purchase #5	$197.44	8.147%	$213.5254	$213.53	$213.55	$213.50
Purchase #6	$67.32	8.293%	$72.9028	$72.90	$72.90	$72.90
Purchase #7	$11.66	7.496%	$12.534	$12.53	$12.55	$12.50
7 purchase totals =	$487.43		$526.1206	$526.11	$526.10	$526.20