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	$61.78	7.731%	$66.5562	$66.56	$66.55	$66.60
Purchase #2	$164.35	9.272%	$179.5885	$179.59	$179.60	$179.60
Purchase #3	$11.61	5.641%	$12.2649	$12.26	$12.25	$12.30
Purchase #4	$100.66	9.705%	$110.4291	$110.43	$110.45	$110.40
Purchase #5	$153.65	8.398%	$166.5535	$166.55	$166.55	$166.60
Purchase #6	$110.40	9.208%	$120.5656	$120.57	$120.55	$120.60
Purchase #7	$83.72	5.670%	$88.4669	$88.47	$88.45	$88.50
7 purchase totals =	$686.17		$744.4247	$744.43	$744.40	$744.60