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	$174.96	8.648%	$190.0905	$190.09	$190.10	$190.10
Purchase #2	$66.34	4.148%	$69.0918	$69.09	$69.10	$69.10
Purchase #3	$239.76	7.559%	$257.8835	$257.88	$257.90	$257.90
Purchase #4	$153.85	9.807%	$168.9381	$168.94	$168.95	$168.90
Purchase #5	$190.82	4.851%	$200.0767	$200.08	$200.10	$200.10
Purchase #6	$123.63	10.124%	$136.1463	$136.15	$136.15	$136.10
Purchase #7	$54.96	5.422%	$57.9399	$57.94	$57.95	$57.90
7 purchase totals =	$1,004.32		$1,080.1668	$1,080.17	$1,080.25	$1,080.10