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	$115.99	11.495%	$129.3231	$129.32	$129.30	$129.30
Purchase #2	$23.44	5.246%	$24.6697	$24.67	$24.65	$24.70
Purchase #3	$81.89	10.856%	$90.78	$90.78	$90.80	$90.80
Purchase #4	$162.48	10.507%	$179.5518	$179.55	$179.55	$179.60
Purchase #5	$41.68	9.110%	$45.477	$45.48	$45.50	$45.50
Purchase #6	$13.73	11.563%	$15.3176	$15.32	$15.30	$15.30
Purchase #7	$168.82	13.665%	$191.8893	$191.89	$191.90	$191.90
7 purchase totals =	$608.03		$677.0085	$677.01	$677.00	$677.10