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	$59.66	7.783%	$64.3033	$64.30	$64.30	$64.30
Purchase #2	$33.72	6.192%	$35.8079	$35.81	$35.80	$35.80
Purchase #3	$228.62	10.181%	$251.8958	$251.90	$251.90	$251.90
Purchase #4	$147.44	8.419%	$159.853	$159.85	$159.85	$159.90
Purchase #5	$129.92	10.441%	$143.4849	$143.48	$143.50	$143.50
Purchase #6	$164.50	10.756%	$182.1936	$182.19	$182.20	$182.20
Purchase #7	$244.94	5.578%	$258.6028	$258.60	$258.60	$258.60
7 purchase totals =	$1,008.80		$1,096.1413	$1,096.13	$1,096.15	$1,096.20