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	$174.83	6.457%	$186.1188	$186.12	$186.10	$186.10
Purchase #2	$37.85	8.218%	$40.9605	$40.96	$40.95	$41.00
Purchase #3	$159.78	4.827%	$167.4926	$167.49	$167.50	$167.50
Purchase #4	$86.85	11.136%	$96.5216	$96.52	$96.50	$96.50
Purchase #5	$126.91	11.283%	$141.2293	$141.23	$141.25	$141.20
Purchase #6	$12.30	13.491%	$13.9594	$13.96	$13.95	$14.00
Purchase #7	$241.89	3.742%	$250.9415	$250.94	$250.95	$250.90
7 purchase totals =	$840.41		$897.2237	$897.22	$897.20	$897.20