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	$60.45	8.750%	$65.7394	$65.74	$65.75	$65.70
Purchase #2	$65.95	9.305%	$72.0866	$72.09	$72.10	$72.10
Purchase #3	$94.26	6.295%	$100.1937	$100.19	$100.20	$100.20
Purchase #4	$118.51	4.520%	$123.8667	$123.87	$123.85	$123.90
Purchase #5	$152.31	8.785%	$165.6904	$165.69	$165.70	$165.70
Purchase #6	$52.59	8.229%	$56.9176	$56.92	$56.90	$56.90
Purchase #7	$215.89	8.626%	$234.5127	$234.51	$234.50	$234.50
7 purchase totals =	$759.96		$819.0071	$819.01	$819.00	$819.00