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	$68.50	5.324%	$72.1469	$72.15	$72.15	$72.10
Purchase #2	$97.49	12.302%	$109.4832	$109.48	$109.50	$109.50
Purchase #3	$179.54	3.128%	$185.156	$185.16	$185.15	$185.20
Purchase #4	$166.90	12.675%	$188.0546	$188.05	$188.05	$188.10
Purchase #5	$166.78	12.715%	$187.9861	$187.99	$188.00	$188.00
Purchase #6	$98.49	10.129%	$108.4661	$108.47	$108.45	$108.50
Purchase #7	$176.61	6.581%	$188.2327	$188.23	$188.25	$188.20
7 purchase totals =	$954.31		$1,039.5256	$1,039.53	$1,039.55	$1,039.60