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	$64.36	9.578%	$70.5244	$70.52	$70.50	$70.50
Purchase #2	$115.30	4.499%	$120.4873	$120.49	$120.50	$120.50
Purchase #3	$39.26	7.668%	$42.2705	$42.27	$42.25	$42.30
Purchase #4	$165.73	8.267%	$179.4309	$179.43	$179.45	$179.40
Purchase #5	$95.48	5.588%	$100.8154	$100.82	$100.80	$100.80
Purchase #6	$246.39	10.870%	$273.1726	$273.17	$273.15	$273.20
Purchase #7	$151.94	13.195%	$171.9885	$171.99	$172.00	$172.00
7 purchase totals =	$878.46		$958.6896	$958.69	$958.65	$958.70