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	$165.73	4.189%	$172.6724	$172.67	$172.65	$172.70
Purchase #2	$147.92	11.423%	$164.8169	$164.82	$164.80	$164.80
Purchase #3	$141.44	8.729%	$153.7863	$153.79	$153.80	$153.80
Purchase #4	$66.89	13.449%	$75.886	$75.89	$75.90	$75.90
Purchase #5	$156.94	4.517%	$164.029	$164.03	$164.05	$164.00
Purchase #6	$16.88	7.533%	$18.1516	$18.15	$18.15	$18.20
Purchase #7	$59.32	9.485%	$64.9465	$64.95	$64.95	$64.90
7 purchase totals =	$755.12		$814.2887	$814.30	$814.30	$814.30