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	$126.50	5.808%	$133.8471	$133.85	$133.85	$133.80
Purchase #2	$136.41	11.381%	$151.9348	$151.93	$151.95	$151.90
Purchase #3	$34.87	11.777%	$38.9766	$38.98	$39.00	$39.00
Purchase #4	$99.25	12.191%	$111.3496	$111.35	$111.35	$111.30
Purchase #5	$180.37	5.775%	$190.7864	$190.79	$190.80	$190.80
Purchase #6	$93.76	5.569%	$98.9815	$98.98	$99.00	$99.00
Purchase #7	$110.86	11.453%	$123.5568	$123.56	$123.55	$123.60
7 purchase totals =	$782.02		$849.4328	$849.44	$849.50	$849.40