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	$238.72	11.820%	$266.9367	$266.94	$266.95	$266.90
Purchase #2	$144.79	8.704%	$157.3925	$157.39	$157.40	$157.40
Purchase #3	$95.84	4.769%	$100.4106	$100.41	$100.40	$100.40
Purchase #4	$155.76	8.772%	$169.4233	$169.42	$169.40	$169.40
Purchase #5	$242.61	11.452%	$270.3937	$270.39	$270.40	$270.40
Purchase #6	$57.57	7.389%	$61.8238	$61.82	$61.80	$61.80
Purchase #7	$33.60	4.400%	$35.0784	$35.08	$35.10	$35.10
7 purchase totals =	$968.89		$1,061.4590	$1,061.45	$1,061.45	$1,061.40