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	$114.47	9.117%	$124.9062	$124.91	$124.90	$124.90
Purchase #2	$34.37	8.201%	$37.1887	$37.19	$37.20	$37.20
Purchase #3	$6.97	13.369%	$7.9018	$7.90	$7.90	$7.90
Purchase #4	$144.66	5.578%	$152.7291	$152.73	$152.75	$152.70
Purchase #5	$56.43	13.314%	$63.9431	$63.94	$63.95	$63.90
Purchase #6	$18.34	11.684%	$20.4828	$20.48	$20.50	$20.50
Purchase #7	$37.93	8.172%	$41.0296	$41.03	$41.05	$41.00
7 purchase totals =	$413.17		$448.1813	$448.18	$448.25	$448.10