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	$143.91	4.782%	$150.7918	$150.79	$150.80	$150.80
Purchase #2	$70.38	3.784%	$73.0432	$73.04	$73.05	$73.00
Purchase #3	$148.26	13.655%	$168.5049	$168.50	$168.50	$168.50
Purchase #4	$40.91	7.584%	$44.0126	$44.01	$44.00	$44.00
Purchase #5	$43.32	4.468%	$45.2555	$45.26	$45.25	$45.30
Purchase #6	$88.86	12.154%	$99.66	$99.66	$99.65	$99.70
Purchase #7	$50.66	4.120%	$52.7472	$52.75	$52.75	$52.70
7 purchase totals =	$586.30		$634.0152	$634.01	$634.00	$634.00