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	$51.65	7.430%	$55.4876	$55.49	$55.50	$55.50
Purchase #2	$159.92	9.601%	$175.2739	$175.27	$175.25	$175.30
Purchase #3	$194.99	11.590%	$217.5893	$217.59	$217.60	$217.60
Purchase #4	$106.89	13.149%	$120.945	$120.95	$120.95	$120.90
Purchase #5	$187.58	12.322%	$210.6936	$210.69	$210.70	$210.70
Purchase #6	$81.95	10.557%	$90.6015	$90.60	$90.60	$90.60
Purchase #7	$217.48	12.339%	$244.3149	$244.31	$244.30	$244.30
7 purchase totals =	$1,000.46		$1,114.9058	$1,114.90	$1,114.90	$1,114.90