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	$32.30	9.628%	$35.4098	$35.41	$35.40	$35.40
Purchase #2	$148.36	13.164%	$167.8901	$167.89	$167.90	$167.90
Purchase #3	$151.78	10.780%	$168.1419	$168.14	$168.15	$168.10
Purchase #4	$42.53	13.267%	$48.1725	$48.17	$48.15	$48.20
Purchase #5	$208.49	9.507%	$228.3111	$228.31	$228.30	$228.30
Purchase #6	$210.40	12.113%	$235.8858	$235.89	$235.90	$235.90
Purchase #7	$108.87	12.645%	$122.6366	$122.64	$122.65	$122.60
7 purchase totals =	$902.73		$1,006.4478	$1,006.45	$1,006.45	$1,006.40