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	$72.49	13.304%	$82.1341	$82.13	$82.15	$82.10
Purchase #2	$99.76	4.277%	$104.0267	$104.03	$104.05	$104.00
Purchase #3	$232.47	8.782%	$252.8855	$252.89	$252.90	$252.90
Purchase #4	$85.74	3.808%	$89.005	$89.01	$89.00	$89.00
Purchase #5	$159.58	7.818%	$172.056	$172.06	$172.05	$172.10
Purchase #6	$65.73	5.872%	$69.5897	$69.59	$69.60	$69.60
Purchase #7	$40.31	10.407%	$44.5051	$44.51	$44.50	$44.50
7 purchase totals =	$756.08		$814.2021	$814.22	$814.25	$814.20