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	$139.87	3.220%	$144.3738	$144.37	$144.35	$144.40
Purchase #2	$12.39	9.221%	$13.5325	$13.53	$13.55	$13.50
Purchase #3	$169.41	12.491%	$190.571	$190.57	$190.55	$190.60
Purchase #4	$189.29	3.796%	$196.4754	$196.48	$196.50	$196.50
Purchase #5	$230.58	13.790%	$262.377	$262.38	$262.40	$262.40
Purchase #6	$72.44	4.175%	$75.4644	$75.46	$75.45	$75.50
Purchase #7	$244.40	8.350%	$264.8074	$264.81	$264.80	$264.80
7 purchase totals =	$1,058.38		$1,147.6015	$1,147.60	$1,147.60	$1,147.70