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	$201.88	6.539%	$215.0809	$215.08	$215.10	$215.10
Purchase #2	$241.86	13.444%	$274.3757	$274.38	$274.40	$274.40
Purchase #3	$10.48	3.576%	$10.8548	$10.85	$10.85	$10.90
Purchase #4	$127.98	6.664%	$136.5086	$136.51	$136.50	$136.50
Purchase #5	$217.59	13.582%	$247.1431	$247.14	$247.15	$247.10
Purchase #6	$106.93	3.684%	$110.8693	$110.87	$110.85	$110.90
Purchase #7	$10.31	5.581%	$10.8854	$10.89	$10.90	$10.90
7 purchase totals =	$917.03		$1,005.7178	$1,005.72	$1,005.75	$1,005.80