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	$225.28	11.247%	$250.6172	$250.62	$250.60	$250.60
Purchase #2	$59.82	7.670%	$64.4082	$64.41	$64.40	$64.40
Purchase #3	$110.47	8.473%	$119.8301	$119.83	$119.85	$119.80
Purchase #4	$52.25	9.299%	$57.1087	$57.11	$57.10	$57.10
Purchase #5	$233.27	12.684%	$262.858	$262.86	$262.85	$262.90
Purchase #6	$81.76	7.626%	$87.995	$88.00	$88.00	$88.00
Purchase #7	$194.40	3.341%	$200.8949	$200.89	$200.90	$200.90
7 purchase totals =	$957.25		$1,043.7121	$1,043.72	$1,043.70	$1,043.70