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	$192.60	7.333%	$206.7234	$206.72	$206.70	$206.70
Purchase #2	$87.94	8.747%	$95.6321	$95.63	$95.65	$95.60
Purchase #3	$11.65	9.749%	$12.7858	$12.79	$12.80	$12.80
Purchase #4	$80.94	11.506%	$90.253	$90.25	$90.25	$90.30
Purchase #5	$163.76	10.120%	$180.3325	$180.33	$180.35	$180.30
Purchase #6	$172.75	7.225%	$185.2312	$185.23	$185.25	$185.20
Purchase #7	$31.60	5.782%	$33.4271	$33.43	$33.45	$33.40
7 purchase totals =	$741.24		$804.3851	$804.38	$804.45	$804.30