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	$52.39	3.432%	$54.188	$54.19	$54.20	$54.20
Purchase #2	$186.49	5.355%	$196.4765	$196.48	$196.50	$196.50
Purchase #3	$214.45	6.577%	$228.5544	$228.55	$228.55	$228.60
Purchase #4	$30.36	3.504%	$31.4238	$31.42	$31.40	$31.40
Purchase #5	$15.75	11.549%	$17.569	$17.57	$17.55	$17.60
Purchase #6	$239.85	12.526%	$269.8936	$269.89	$269.90	$269.90
Purchase #7	$96.50	12.219%	$108.2913	$108.29	$108.30	$108.30
7 purchase totals =	$835.79		$906.3966	$906.39	$906.40	$906.50