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	$247.25	11.865%	$276.5862	$276.59	$276.60	$276.60
Purchase #2	$112.70	10.691%	$124.7488	$124.75	$124.75	$124.70
Purchase #3	$63.42	12.503%	$71.3494	$71.35	$71.35	$71.30
Purchase #4	$172.32	5.630%	$182.0216	$182.02	$182.00	$182.00
Purchase #5	$135.59	5.812%	$143.4705	$143.47	$143.45	$143.50
Purchase #6	$211.46	3.799%	$219.4934	$219.49	$219.50	$219.50
Purchase #7	$185.79	3.266%	$191.8579	$191.86	$191.85	$191.90
7 purchase totals =	$1,128.53		$1,209.5278	$1,209.53	$1,209.50	$1,209.50