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	$170.69	4.317%	$178.0587	$178.06	$178.05	$178.10
Purchase #2	$250.88	12.623%	$282.5486	$282.55	$282.55	$282.50
Purchase #3	$189.94	10.358%	$209.614	$209.61	$209.60	$209.60
Purchase #4	$109.59	6.462%	$116.6717	$116.67	$116.65	$116.70
Purchase #5	$32.86	8.155%	$35.5397	$35.54	$35.55	$35.50
Purchase #6	$97.55	6.661%	$104.0478	$104.05	$104.05	$104.00
Purchase #7	$242.59	13.155%	$274.5027	$274.50	$274.50	$274.50
7 purchase totals =	$1,094.10		$1,200.9832	$1,200.98	$1,200.95	$1,200.90