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	$81.53	3.163%	$84.1088	$84.11	$84.10	$84.10
Purchase #2	$113.48	12.527%	$127.6956	$127.70	$127.70	$127.70
Purchase #3	$153.88	5.596%	$162.4911	$162.49	$162.50	$162.50
Purchase #4	$82.29	4.122%	$85.682	$85.68	$85.70	$85.70
Purchase #5	$100.36	11.545%	$111.9466	$111.95	$111.95	$111.90
Purchase #6	$98.27	6.591%	$104.747	$104.75	$104.75	$104.70
Purchase #7	$186.31	11.809%	$208.3113	$208.31	$208.30	$208.30
7 purchase totals =	$816.12		$884.9824	$884.99	$885.00	$884.90