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	$164.86	5.209%	$173.4476	$173.45	$173.45	$173.40
Purchase #2	$177.37	8.156%	$191.8363	$191.84	$191.85	$191.80
Purchase #3	$16.89	10.670%	$18.6922	$18.69	$18.70	$18.70
Purchase #4	$213.87	12.226%	$240.0177	$240.02	$240.00	$240.00
Purchase #5	$191.79	12.421%	$215.6122	$215.61	$215.60	$215.60
Purchase #6	$219.36	11.144%	$243.8055	$243.81	$243.80	$243.80
Purchase #7	$64.39	11.856%	$72.0241	$72.02	$72.00	$72.00
7 purchase totals =	$1,048.53		$1,155.4356	$1,155.44	$1,155.40	$1,155.30