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	$54.66	12.222%	$61.3405	$61.34	$61.35	$61.30
Purchase #2	$169.47	7.719%	$182.5514	$182.55	$182.55	$182.60
Purchase #3	$63.38	9.376%	$69.3225	$69.32	$69.30	$69.30
Purchase #4	$126.40	10.632%	$139.8388	$139.84	$139.85	$139.80
Purchase #5	$35.94	4.228%	$37.4595	$37.46	$37.45	$37.50
Purchase #6	$242.68	8.521%	$263.3588	$263.36	$263.35	$263.40
Purchase #7	$241.28	12.526%	$271.5027	$271.50	$271.50	$271.50
7 purchase totals =	$933.81		$1,025.3742	$1,025.37	$1,025.35	$1,025.40