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	$122.66	7.418%	$131.7589	$131.76	$131.75	$131.80
Purchase #2	$53.77	10.242%	$59.2771	$59.28	$59.30	$59.30
Purchase #3	$71.95	8.712%	$78.2183	$78.22	$78.20	$78.20
Purchase #4	$175.46	5.373%	$184.8875	$184.89	$184.90	$184.90
Purchase #5	$34.96	11.455%	$38.9647	$38.96	$38.95	$39.00
Purchase #6	$39.34	6.487%	$41.892	$41.89	$41.90	$41.90
Purchase #7	$169.48	3.853%	$176.0101	$176.01	$176.00	$176.00
7 purchase totals =	$667.62		$711.0086	$711.01	$711.00	$711.10