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	$187.72	5.859%	$198.7185	$198.72	$198.70	$198.70
Purchase #2	$205.85	4.642%	$215.4056	$215.41	$215.40	$215.40
Purchase #3	$27.91	12.743%	$31.4666	$31.47	$31.45	$31.50
Purchase #4	$28.82	13.340%	$32.6646	$32.66	$32.65	$32.70
Purchase #5	$24.36	5.103%	$25.6031	$25.60	$25.60	$25.60
Purchase #6	$89.76	5.183%	$94.4123	$94.41	$94.40	$94.40
Purchase #7	$105.27	7.693%	$113.3684	$113.37	$113.35	$113.40
7 purchase totals =	$669.69		$711.6391	$711.64	$711.55	$711.70