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	$48.89	13.110%	$55.2995	$55.30	$55.30	$55.30
Purchase #2	$211.54	3.684%	$219.3331	$219.33	$219.35	$219.30
Purchase #3	$184.81	5.840%	$195.6029	$195.60	$195.60	$195.60
Purchase #4	$86.84	3.313%	$89.717	$89.72	$89.70	$89.70
Purchase #5	$40.36	7.522%	$43.3959	$43.40	$43.40	$43.40
Purchase #6	$136.31	13.659%	$154.9286	$154.93	$154.95	$154.90
Purchase #7	$5.82	7.552%	$6.2595	$6.26	$6.25	$6.30
7 purchase totals =	$714.57		$764.5365	$764.54	$764.55	$764.50