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	$99.54	3.827%	$103.3494	$103.35	$103.35	$103.30
Purchase #2	$189.52	3.661%	$196.4583	$196.46	$196.45	$196.50
Purchase #3	$125.65	12.212%	$140.9944	$140.99	$141.00	$141.00
Purchase #4	$164.41	9.284%	$179.6738	$179.67	$179.65	$179.70
Purchase #5	$88.80	11.169%	$98.7181	$98.72	$98.70	$98.70
Purchase #6	$97.41	3.402%	$100.7239	$100.72	$100.70	$100.70
Purchase #7	$202.60	6.145%	$215.0498	$215.05	$215.05	$215.00
7 purchase totals =	$967.93		$1,034.9677	$1,034.96	$1,034.90	$1,034.90