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	$178.59	12.732%	$201.3281	$201.33	$201.35	$201.30
Purchase #2	$128.27	10.567%	$141.8243	$141.82	$141.80	$141.80
Purchase #3	$99.67	13.845%	$113.4693	$113.47	$113.45	$113.50
Purchase #4	$186.55	7.629%	$200.7819	$200.78	$200.80	$200.80
Purchase #5	$141.58	6.719%	$151.0928	$151.09	$151.10	$151.10
Purchase #6	$162.27	11.496%	$180.9246	$180.92	$180.90	$180.90
Purchase #7	$48.71	8.188%	$52.6984	$52.70	$52.70	$52.70
7 purchase totals =	$945.64		$1,042.1194	$1,042.11	$1,042.10	$1,042.10