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	$198.54	9.600%	$217.5998	$217.60	$217.60	$217.60
Purchase #2	$165.40	12.283%	$185.7161	$185.72	$185.70	$185.70
Purchase #3	$153.36	12.478%	$172.4963	$172.50	$172.50	$172.50
Purchase #4	$211.57	5.322%	$222.8298	$222.83	$222.85	$222.80
Purchase #5	$153.27	10.845%	$169.8921	$169.89	$169.90	$169.90
Purchase #6	$40.53	4.498%	$42.353	$42.35	$42.35	$42.40
Purchase #7	$43.45	5.829%	$45.9827	$45.98	$46.00	$46.00
7 purchase totals =	$966.12		$1,056.8698	$1,056.87	$1,056.90	$1,056.90