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	$99.29	12.281%	$111.4838	$111.48	$111.50	$111.50
Purchase #2	$181.46	5.747%	$191.8885	$191.89	$191.90	$191.90
Purchase #3	$83.98	5.400%	$88.5149	$88.51	$88.50	$88.50
Purchase #4	$95.34	13.785%	$108.4826	$108.48	$108.50	$108.50
Purchase #5	$134.50	10.193%	$148.2096	$148.21	$148.20	$148.20
Purchase #6	$171.87	7.212%	$184.2653	$184.27	$184.25	$184.30
Purchase #7	$247.62	10.207%	$272.8946	$272.89	$272.90	$272.90
7 purchase totals =	$1,014.06		$1,105.7393	$1,105.73	$1,105.75	$1,105.80