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	$227.91	9.316%	$249.1421	$249.14	$249.15	$249.10
Purchase #2	$18.35	3.678%	$19.0249	$19.02	$19.00	$19.00
Purchase #3	$22.51	13.333%	$25.5113	$25.51	$25.50	$25.50
Purchase #4	$111.73	3.455%	$115.5903	$115.59	$115.60	$115.60
Purchase #5	$230.61	8.754%	$250.7976	$250.80	$250.80	$250.80
Purchase #6	$150.36	10.502%	$166.1508	$166.15	$166.15	$166.20
Purchase #7	$199.42	11.467%	$222.2875	$222.29	$222.30	$222.30
7 purchase totals =	$960.89		$1,048.5045	$1,048.50	$1,048.50	$1,048.50