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	$117.37	4.794%	$122.9967	$123.00	$123.00	$123.00
Purchase #2	$158.46	8.860%	$172.4996	$172.50	$172.50	$172.50
Purchase #3	$151.72	13.786%	$172.6361	$172.64	$172.65	$172.60
Purchase #4	$223.67	8.335%	$242.3129	$242.31	$242.30	$242.30
Purchase #5	$191.35	11.765%	$213.8623	$213.86	$213.85	$213.90
Purchase #6	$34.39	6.716%	$36.6996	$36.70	$36.70	$36.70
Purchase #7	$249.36	4.646%	$260.9453	$260.95	$260.95	$260.90
7 purchase totals =	$1,126.32		$1,221.9525	$1,221.96	$1,221.95	$1,221.90