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	$77.92	5.292%	$82.0435	$82.04	$82.05	$82.00
Purchase #2	$83.66	6.814%	$89.3606	$89.36	$89.35	$89.40
Purchase #3	$238.99	11.481%	$266.4284	$266.43	$266.45	$266.40
Purchase #4	$151.42	3.248%	$156.3381	$156.34	$156.35	$156.30
Purchase #5	$10.51	9.362%	$11.4939	$11.49	$11.50	$11.50
Purchase #6	$112.73	11.848%	$126.0863	$126.09	$126.10	$126.10
Purchase #7	$91.65	9.591%	$100.4402	$100.44	$100.45	$100.40
7 purchase totals =	$766.88		$832.1910	$832.19	$832.25	$832.10