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	$98.54	6.360%	$104.8071	$104.81	$104.80	$104.80
Purchase #2	$218.45	12.186%	$245.0703	$245.07	$245.05	$245.10
Purchase #3	$76.97	13.252%	$87.1701	$87.17	$87.15	$87.20
Purchase #4	$209.46	3.764%	$217.3441	$217.34	$217.35	$217.30
Purchase #5	$143.54	13.124%	$162.3782	$162.38	$162.40	$162.40
Purchase #6	$184.96	7.845%	$199.4701	$199.47	$199.45	$199.50
Purchase #7	$118.38	7.336%	$127.0644	$127.06	$127.05	$127.10
7 purchase totals =	$1,050.30		$1,143.3043	$1,143.30	$1,143.25	$1,143.40