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	$66.67	7.336%	$71.5609	$71.56	$71.55	$71.60
Purchase #2	$196.52	12.766%	$221.6077	$221.61	$221.60	$221.60
Purchase #3	$126.71	12.323%	$142.3245	$142.32	$142.30	$142.30
Purchase #4	$96.46	7.497%	$103.6916	$103.69	$103.70	$103.70
Purchase #5	$241.73	7.580%	$260.0531	$260.05	$260.05	$260.10
Purchase #6	$169.87	9.756%	$186.4425	$186.44	$186.45	$186.40
Purchase #7	$145.66	3.213%	$150.3401	$150.34	$150.35	$150.30
7 purchase totals =	$1,043.62		$1,136.0204	$1,136.01	$1,136.00	$1,136.00