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	$247.33	4.698%	$258.9496	$258.95	$258.95	$258.90
Purchase #2	$87.68	12.164%	$98.3454	$98.35	$98.35	$98.30
Purchase #3	$158.74	9.214%	$173.3663	$173.37	$173.35	$173.40
Purchase #4	$24.26	12.219%	$27.2243	$27.22	$27.20	$27.20
Purchase #5	$171.88	4.271%	$179.221	$179.22	$179.20	$179.20
Purchase #6	$231.81	11.478%	$258.4172	$258.42	$258.40	$258.40
Purchase #7	$86.64	3.759%	$89.8968	$89.90	$89.90	$89.90
7 purchase totals =	$1,008.34		$1,085.4206	$1,085.43	$1,085.35	$1,085.30