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	$250.58	4.756%	$262.4976	$262.50	$262.50	$262.50
Purchase #2	$217.53	10.473%	$240.3119	$240.31	$240.30	$240.30
Purchase #3	$204.27	5.253%	$215.0003	$215.00	$215.00	$215.00
Purchase #4	$238.67	8.638%	$259.2863	$259.29	$259.30	$259.30
Purchase #5	$75.96	13.561%	$86.2609	$86.26	$86.25	$86.30
Purchase #6	$222.86	9.433%	$243.8824	$243.88	$243.90	$243.90
Purchase #7	$179.88	7.242%	$192.9069	$192.91	$192.90	$192.90
7 purchase totals =	$1,389.75		$1,500.1463	$1,500.15	$1,500.15	$1,500.20