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	$132.63	9.231%	$144.8731	$144.87	$144.85	$144.90
Purchase #2	$154.76	13.734%	$176.0147	$176.01	$176.00	$176.00
Purchase #3	$81.58	7.238%	$87.4848	$87.48	$87.50	$87.50
Purchase #4	$206.58	7.663%	$222.4102	$222.41	$222.40	$222.40
Purchase #5	$70.89	12.679%	$79.8781	$79.88	$79.90	$79.90
Purchase #6	$78.65	8.198%	$85.0977	$85.10	$85.10	$85.10
Purchase #7	$180.44	11.295%	$200.8207	$200.82	$200.80	$200.80
7 purchase totals =	$905.53		$996.5793	$996.57	$996.55	$996.60