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	$41.89	3.176%	$43.2204	$43.22	$43.20	$43.20
Purchase #2	$40.82	6.476%	$43.4635	$43.46	$43.45	$43.50
Purchase #3	$96.98	13.318%	$109.8958	$109.90	$109.90	$109.90
Purchase #4	$159.44	7.576%	$171.5192	$171.52	$171.50	$171.50
Purchase #5	$235.65	4.609%	$246.5111	$246.51	$246.50	$246.50
Purchase #6	$179.69	10.470%	$198.5035	$198.50	$198.50	$198.50
Purchase #7	$73.95	6.218%	$78.5482	$78.55	$78.55	$78.50
7 purchase totals =	$828.42		$891.6617	$891.66	$891.60	$891.60