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	$129.38	13.777%	$147.2047	$147.20	$147.20	$147.20
Purchase #2	$250.56	10.320%	$276.4178	$276.42	$276.40	$276.40
Purchase #3	$31.52	3.655%	$32.6721	$32.67	$32.65	$32.70
Purchase #4	$213.70	5.448%	$225.3424	$225.34	$225.35	$225.30
Purchase #5	$150.63	11.824%	$168.4405	$168.44	$168.45	$168.40
Purchase #6	$161.85	4.735%	$169.5136	$169.51	$169.50	$169.50
Purchase #7	$98.60	13.184%	$111.5994	$111.60	$111.60	$111.60
7 purchase totals =	$1,036.24		$1,131.1905	$1,131.18	$1,131.15	$1,131.10