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	$110.44	7.605%	$118.839	$118.84	$118.85	$118.80
Purchase #2	$238.60	7.121%	$255.5907	$255.59	$255.60	$255.60
Purchase #3	$147.83	13.802%	$168.2335	$168.23	$168.25	$168.20
Purchase #4	$189.50	7.799%	$204.2791	$204.28	$204.30	$204.30
Purchase #5	$33.50	10.293%	$36.9482	$36.95	$36.95	$36.90
Purchase #6	$241.43	13.783%	$274.7063	$274.71	$274.70	$274.70
Purchase #7	$63.93	13.721%	$72.7018	$72.70	$72.70	$72.70
7 purchase totals =	$1,025.23		$1,131.2986	$1,131.30	$1,131.35	$1,131.20