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	$195.66	12.174%	$219.4796	$219.48	$219.50	$219.50
Purchase #2	$156.43	9.444%	$171.2032	$171.20	$171.20	$171.20
Purchase #3	$154.83	6.729%	$165.2485	$165.25	$165.25	$165.20
Purchase #4	$31.62	5.523%	$33.3664	$33.37	$33.35	$33.40
Purchase #5	$114.60	7.612%	$123.3234	$123.32	$123.30	$123.30
Purchase #6	$131.51	7.338%	$141.1602	$141.16	$141.15	$141.20
Purchase #7	$122.37	5.844%	$129.5213	$129.52	$129.50	$129.50
7 purchase totals =	$907.02		$983.3026	$983.30	$983.25	$983.30