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	$93.73	9.516%	$102.6493	$102.65	$102.65	$102.60
Purchase #2	$35.60	8.669%	$38.6862	$38.69	$38.70	$38.70
Purchase #3	$155.65	8.213%	$168.4335	$168.43	$168.45	$168.40
Purchase #4	$43.27	12.261%	$48.5753	$48.58	$48.60	$48.60
Purchase #5	$45.31	13.216%	$51.2982	$51.30	$51.30	$51.30
Purchase #6	$230.31	6.330%	$244.8886	$244.89	$244.90	$244.90
Purchase #7	$238.95	10.736%	$264.6037	$264.60	$264.60	$264.60
7 purchase totals =	$842.82		$919.1348	$919.14	$919.20	$919.10