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	$250.32	4.282%	$261.0387	$261.04	$261.05	$261.00
Purchase #2	$190.76	13.398%	$216.318	$216.32	$216.30	$216.30
Purchase #3	$95.59	8.312%	$103.5354	$103.54	$103.55	$103.50
Purchase #4	$108.27	13.621%	$123.0175	$123.02	$123.00	$123.00
Purchase #5	$217.41	8.373%	$235.6137	$235.61	$235.60	$235.60
Purchase #6	$19.88	6.497%	$21.1716	$21.17	$21.15	$21.20
Purchase #7	$179.67	4.121%	$187.0742	$187.07	$187.05	$187.10
7 purchase totals =	$1,061.90		$1,147.7691	$1,147.77	$1,147.70	$1,147.70