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	$175.41	8.546%	$190.4005	$190.40	$190.40	$190.40
Purchase #2	$156.75	9.537%	$171.6992	$171.70	$171.70	$171.70
Purchase #3	$213.72	11.587%	$238.4837	$238.48	$238.50	$238.50
Purchase #4	$69.39	11.401%	$77.3012	$77.30	$77.30	$77.30
Purchase #5	$71.96	11.792%	$80.4455	$80.45	$80.45	$80.40
Purchase #6	$230.97	13.222%	$261.5089	$261.51	$261.50	$261.50
Purchase #7	$123.65	8.620%	$134.3086	$134.31	$134.30	$134.30
7 purchase totals =	$1,041.85		$1,154.1476	$1,154.15	$1,154.15	$1,154.10