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	$212.48	10.458%	$234.7012	$234.70	$234.70	$234.70
Purchase #2	$82.41	10.295%	$90.8941	$90.89	$90.90	$90.90
Purchase #3	$38.42	5.307%	$40.4589	$40.46	$40.45	$40.50
Purchase #4	$196.64	7.821%	$212.0192	$212.02	$212.00	$212.00
Purchase #5	$198.42	5.339%	$209.0136	$209.01	$209.00	$209.00
Purchase #6	$157.92	11.196%	$175.6007	$175.60	$175.60	$175.60
Purchase #7	$139.61	13.523%	$158.4895	$158.49	$158.50	$158.50
7 purchase totals =	$1,025.90		$1,121.1772	$1,121.17	$1,121.15	$1,121.20