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	$217.48	10.490%	$240.2937	$240.29	$240.30	$240.30
Purchase #2	$97.36	7.258%	$104.4264	$104.43	$104.45	$104.40
Purchase #3	$213.57	7.503%	$229.5942	$229.59	$229.60	$229.60
Purchase #4	$167.38	13.534%	$190.0332	$190.03	$190.05	$190.00
Purchase #5	$12.81	10.695%	$14.18	$14.18	$14.20	$14.20
Purchase #6	$219.35	12.346%	$246.431	$246.43	$246.45	$246.40
Purchase #7	$242.42	13.791%	$275.8521	$275.85	$275.85	$275.90
7 purchase totals =	$1,170.37		$1,300.8106	$1,300.80	$1,300.90	$1,300.80