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	$233.91	12.313%	$262.7113	$262.71	$262.70	$262.70
Purchase #2	$153.51	7.460%	$164.9618	$164.96	$164.95	$165.00
Purchase #3	$25.37	11.679%	$28.333	$28.33	$28.35	$28.30
Purchase #4	$198.89	3.242%	$205.338	$205.34	$205.35	$205.30
Purchase #5	$201.29	7.537%	$216.4612	$216.46	$216.45	$216.50
Purchase #6	$64.65	11.706%	$72.2179	$72.22	$72.20	$72.20
Purchase #7	$97.38	5.660%	$102.8917	$102.89	$102.90	$102.90
7 purchase totals =	$975.00		$1,052.9149	$1,052.91	$1,052.90	$1,052.90