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	$112.73	10.317%	$124.3604	$124.36	$124.35	$124.40
Purchase #2	$11.96	11.323%	$13.3142	$13.31	$13.30	$13.30
Purchase #3	$50.89	11.113%	$56.5454	$56.55	$56.55	$56.50
Purchase #4	$58.54	12.555%	$65.8897	$65.89	$65.90	$65.90
Purchase #5	$240.85	12.855%	$271.8113	$271.81	$271.80	$271.80
Purchase #6	$114.55	4.289%	$119.463	$119.46	$119.45	$119.50
Purchase #7	$164.29	6.342%	$174.7093	$174.71	$174.70	$174.70
7 purchase totals =	$753.81		$826.0933	$826.09	$826.05	$826.10