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	$246.31	6.754%	$262.9458	$262.95	$262.95	$262.90
Purchase #2	$180.78	6.469%	$192.4747	$192.47	$192.45	$192.50
Purchase #3	$192.56	8.787%	$209.4802	$209.48	$209.50	$209.50
Purchase #4	$180.76	10.104%	$199.024	$199.02	$199.00	$199.00
Purchase #5	$70.82	10.150%	$78.0082	$78.01	$78.00	$78.00
Purchase #6	$151.97	10.746%	$168.3007	$168.30	$168.30	$168.30
Purchase #7	$99.71	13.126%	$112.7979	$112.80	$112.80	$112.80
7 purchase totals =	$1,122.91		$1,223.0315	$1,223.03	$1,223.00	$1,223.00