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	$29.42	11.562%	$32.8215	$32.82	$32.80	$32.80
Purchase #2	$170.72	11.337%	$190.0745	$190.07	$190.05	$190.10
Purchase #3	$193.57	8.159%	$209.3634	$209.36	$209.35	$209.40
Purchase #4	$86.64	3.257%	$89.4619	$89.46	$89.45	$89.50
Purchase #5	$108.73	13.686%	$123.6108	$123.61	$123.60	$123.60
Purchase #6	$165.64	12.768%	$186.7889	$186.79	$186.80	$186.80
Purchase #7	$194.53	5.427%	$205.0871	$205.09	$205.10	$205.10
7 purchase totals =	$949.25		$1,037.2081	$1,037.20	$1,037.15	$1,037.30