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	$54.96	8.861%	$59.83	$59.83	$59.85	$59.80
Purchase #2	$168.43	5.155%	$177.1126	$177.11	$177.10	$177.10
Purchase #3	$210.44	13.177%	$238.1697	$238.17	$238.15	$238.20
Purchase #4	$136.83	6.465%	$145.6761	$145.68	$145.70	$145.70
Purchase #5	$106.27	9.334%	$116.1892	$116.19	$116.20	$116.20
Purchase #6	$35.47	6.119%	$37.6404	$37.64	$37.65	$37.60
Purchase #7	$231.31	9.655%	$253.643	$253.64	$253.65	$253.60
7 purchase totals =	$943.71		$1,028.2610	$1,028.26	$1,028.30	$1,028.20