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	$179.93	13.873%	$204.8917	$204.89	$204.90	$204.90
Purchase #2	$80.55	12.326%	$90.4786	$90.48	$90.50	$90.50
Purchase #3	$148.34	11.492%	$165.3872	$165.39	$165.40	$165.40
Purchase #4	$179.57	7.601%	$193.2191	$193.22	$193.20	$193.20
Purchase #5	$172.77	13.632%	$196.322	$196.32	$196.30	$196.30
Purchase #6	$119.87	5.401%	$126.3442	$126.34	$126.35	$126.30
Purchase #7	$197.71	10.693%	$218.8511	$218.85	$218.85	$218.90
7 purchase totals =	$1,078.74		$1,195.4939	$1,195.49	$1,195.50	$1,195.50