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	$174.66	8.761%	$189.962	$189.96	$189.95	$190.00
Purchase #2	$231.69	13.298%	$262.5001	$262.50	$262.50	$262.50
Purchase #3	$171.97	10.460%	$189.9581	$189.96	$189.95	$190.00
Purchase #4	$226.82	13.143%	$256.631	$256.63	$256.65	$256.60
Purchase #5	$155.95	8.111%	$168.5991	$168.60	$168.60	$168.60
Purchase #6	$152.60	12.452%	$171.6018	$171.60	$171.60	$171.60
Purchase #7	$189.27	10.822%	$209.7528	$209.75	$209.75	$209.80
7 purchase totals =	$1,302.96		$1,449.0049	$1,449.00	$1,449.00	$1,449.10