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	$205.56	4.529%	$214.8698	$214.87	$214.85	$214.90
Purchase #2	$138.71	9.526%	$151.9235	$151.92	$151.90	$151.90
Purchase #3	$140.51	8.626%	$152.6304	$152.63	$152.65	$152.60
Purchase #4	$233.38	11.818%	$260.9608	$260.96	$260.95	$261.00
Purchase #5	$18.77	11.229%	$20.8777	$20.88	$20.90	$20.90
Purchase #6	$246.89	8.843%	$268.7225	$268.72	$268.70	$268.70
Purchase #7	$126.28	13.179%	$142.9224	$142.92	$142.90	$142.90
7 purchase totals =	$1,110.10		$1,212.9071	$1,212.90	$1,212.85	$1,212.90