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	$217.67	11.407%	$242.4996	$242.50	$242.50	$242.50
Purchase #2	$104.38	13.122%	$118.0767	$118.08	$118.10	$118.10
Purchase #3	$46.42	8.741%	$50.4776	$50.48	$50.50	$50.50
Purchase #4	$142.73	4.801%	$149.5825	$149.58	$149.60	$149.60
Purchase #5	$24.38	11.846%	$27.2681	$27.27	$27.25	$27.30
Purchase #6	$31.53	13.858%	$35.8994	$35.90	$35.90	$35.90
Purchase #7	$70.78	9.565%	$77.5501	$77.55	$77.55	$77.60
7 purchase totals =	$637.89		$701.3540	$701.36	$701.40	$701.50