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	$133.94	5.595%	$141.4339	$141.43	$141.45	$141.40
Purchase #2	$200.31	5.533%	$211.3932	$211.39	$211.40	$211.40
Purchase #3	$109.41	9.597%	$119.9101	$119.91	$119.90	$119.90
Purchase #4	$216.41	3.323%	$223.6013	$223.60	$223.60	$223.60
Purchase #5	$85.41	8.141%	$92.3632	$92.36	$92.35	$92.40
Purchase #6	$19.53	11.489%	$21.7738	$21.77	$21.75	$21.80
Purchase #7	$151.38	8.500%	$164.2473	$164.25	$164.25	$164.20
7 purchase totals =	$916.39		$974.7228	$974.71	$974.70	$974.70