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	$32.63	13.457%	$37.021	$37.02	$37.00	$37.00
Purchase #2	$74.52	5.182%	$78.3816	$78.38	$78.40	$78.40
Purchase #3	$232.38	4.104%	$241.9169	$241.92	$241.90	$241.90
Purchase #4	$181.73	3.336%	$187.7925	$187.79	$187.80	$187.80
Purchase #5	$229.37	5.408%	$241.7743	$241.77	$241.75	$241.80
Purchase #6	$143.70	7.739%	$154.8209	$154.82	$154.80	$154.80
Purchase #7	$39.93	8.469%	$43.3117	$43.31	$43.30	$43.30
7 purchase totals =	$934.26		$985.0189	$985.01	$984.95	$985.00