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	$209.29	10.275%	$230.7945	$230.79	$230.80	$230.80
Purchase #2	$247.25	4.192%	$257.6147	$257.61	$257.60	$257.60
Purchase #3	$86.57	9.746%	$95.0071	$95.01	$95.00	$95.00
Purchase #4	$162.39	4.189%	$169.1925	$169.19	$169.20	$169.20
Purchase #5	$31.36	13.321%	$35.5375	$35.54	$35.55	$35.50
Purchase #6	$99.56	6.135%	$105.668	$105.67	$105.65	$105.70
Purchase #7	$89.89	7.602%	$96.7234	$96.72	$96.70	$96.70
7 purchase totals =	$926.31		$990.5377	$990.53	$990.50	$990.50