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	$42.74	12.534%	$48.097	$48.10	$48.10	$48.10
Purchase #2	$220.86	10.532%	$244.121	$244.12	$244.10	$244.10
Purchase #3	$80.73	12.527%	$90.843	$90.84	$90.85	$90.80
Purchase #4	$63.60	13.395%	$72.1192	$72.12	$72.10	$72.10
Purchase #5	$85.71	13.749%	$97.4943	$97.49	$97.50	$97.50
Purchase #6	$217.32	6.760%	$232.0108	$232.01	$232.00	$232.00
Purchase #7	$120.55	6.678%	$128.6003	$128.60	$128.60	$128.60
7 purchase totals =	$831.51		$913.2856	$913.28	$913.25	$913.20