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	$114.65	5.384%	$120.8228	$120.82	$120.80	$120.80
Purchase #2	$95.63	3.472%	$98.9503	$98.95	$98.95	$99.00
Purchase #3	$250.93	7.611%	$270.0283	$270.03	$270.05	$270.00
Purchase #4	$232.66	10.157%	$256.2913	$256.29	$256.30	$256.30
Purchase #5	$137.81	10.527%	$152.3173	$152.32	$152.30	$152.30
Purchase #6	$140.58	8.181%	$152.0808	$152.08	$152.10	$152.10
Purchase #7	$132.47	5.320%	$139.5174	$139.52	$139.50	$139.50
7 purchase totals =	$1,104.73		$1,190.0082	$1,190.01	$1,190.00	$1,190.00