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	$65.90	5.250%	$69.3598	$69.36	$69.35	$69.40
Purchase #2	$194.75	10.124%	$214.4665	$214.47	$214.45	$214.50
Purchase #3	$143.35	7.707%	$154.398	$154.40	$154.40	$154.40
Purchase #4	$194.59	12.130%	$218.1938	$218.19	$218.20	$218.20
Purchase #5	$207.35	9.682%	$227.4256	$227.43	$227.45	$227.40
Purchase #6	$18.55	12.621%	$20.8912	$20.89	$20.90	$20.90
Purchase #7	$88.71	11.333%	$98.7635	$98.76	$98.75	$98.80
7 purchase totals =	$913.20		$1,003.4984	$1,003.50	$1,003.50	$1,003.60