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	$10.27	8.347%	$11.1272	$11.13	$11.15	$11.10
Purchase #2	$179.30	7.685%	$193.0792	$193.08	$193.10	$193.10
Purchase #3	$70.43	11.300%	$78.3886	$78.39	$78.40	$78.40
Purchase #4	$227.40	10.729%	$251.7977	$251.80	$251.80	$251.80
Purchase #5	$70.71	10.487%	$78.1254	$78.13	$78.15	$78.10
Purchase #6	$161.66	13.871%	$184.0839	$184.08	$184.10	$184.10
Purchase #7	$104.81	4.570%	$109.5998	$109.60	$109.60	$109.60
7 purchase totals =	$824.58		$906.2018	$906.21	$906.30	$906.20