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	$218.53	6.795%	$233.3791	$233.38	$233.40	$233.40
Purchase #2	$163.61	9.383%	$178.9615	$178.96	$178.95	$179.00
Purchase #3	$228.28	7.698%	$245.853	$245.85	$245.85	$245.90
Purchase #4	$158.47	12.269%	$177.9127	$177.91	$177.90	$177.90
Purchase #5	$130.85	9.418%	$143.1735	$143.17	$143.15	$143.20
Purchase #6	$177.62	4.533%	$185.6715	$185.67	$185.65	$185.70
Purchase #7	$28.30	11.455%	$31.5418	$31.54	$31.55	$31.50
7 purchase totals =	$1,105.66		$1,196.4931	$1,196.48	$1,196.45	$1,196.60