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	$109.31	4.669%	$114.4137	$114.41	$114.40	$114.40
Purchase #2	$116.52	12.517%	$131.1048	$131.10	$131.10	$131.10
Purchase #3	$224.37	7.674%	$241.5882	$241.59	$241.60	$241.60
Purchase #4	$224.77	7.366%	$241.3266	$241.33	$241.35	$241.30
Purchase #5	$133.75	5.104%	$140.5766	$140.58	$140.60	$140.60
Purchase #6	$250.31	10.209%	$275.8641	$275.86	$275.85	$275.90
Purchase #7	$236.75	12.508%	$266.3627	$266.36	$266.35	$266.40
7 purchase totals =	$1,295.78		$1,411.2367	$1,411.23	$1,411.25	$1,411.30