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	$211.51	13.237%	$239.5076	$239.51	$239.50	$239.50
Purchase #2	$151.47	6.107%	$160.7203	$160.72	$160.70	$160.70
Purchase #3	$209.56	6.185%	$222.5213	$222.52	$222.50	$222.50
Purchase #4	$184.51	7.779%	$198.863	$198.86	$198.85	$198.90
Purchase #5	$29.72	7.320%	$31.8955	$31.90	$31.90	$31.90
Purchase #6	$35.59	5.243%	$37.456	$37.46	$37.45	$37.50
Purchase #7	$199.69	6.630%	$212.9294	$212.93	$212.95	$212.90
7 purchase totals =	$1,022.05		$1,103.8931	$1,103.90	$1,103.85	$1,103.90