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	$34.41	9.295%	$37.6084	$37.61	$37.60	$37.60
Purchase #2	$168.58	12.632%	$189.875	$189.88	$189.90	$189.90
Purchase #3	$179.53	7.300%	$192.6357	$192.64	$192.65	$192.60
Purchase #4	$181.77	13.656%	$206.5925	$206.59	$206.60	$206.60
Purchase #5	$33.95	4.556%	$35.4968	$35.50	$35.50	$35.50
Purchase #6	$126.36	10.180%	$139.2234	$139.22	$139.20	$139.20
Purchase #7	$155.58	11.825%	$173.9773	$173.98	$174.00	$174.00
7 purchase totals =	$880.18		$975.4091	$975.42	$975.45	$975.40