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	$116.89	12.838%	$131.8963	$131.90	$131.90	$131.90
Purchase #2	$198.90	7.547%	$213.911	$213.91	$213.90	$213.90
Purchase #3	$102.70	11.284%	$114.2887	$114.29	$114.30	$114.30
Purchase #4	$154.77	11.383%	$172.3875	$172.39	$172.40	$172.40
Purchase #5	$136.33	3.481%	$141.0756	$141.08	$141.10	$141.10
Purchase #6	$195.30	7.838%	$210.6076	$210.61	$210.60	$210.60
Purchase #7	$103.36	9.809%	$113.4986	$113.50	$113.50	$113.50
7 purchase totals =	$1,008.25		$1,097.6653	$1,097.68	$1,097.70	$1,097.70