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	$111.79	6.775%	$119.3638	$119.36	$119.35	$119.40
Purchase #2	$158.98	7.791%	$171.3661	$171.37	$171.35	$171.40
Purchase #3	$219.25	4.220%	$228.5024	$228.50	$228.50	$228.50
Purchase #4	$79.66	7.719%	$85.809	$85.81	$85.80	$85.80
Purchase #5	$224.92	11.390%	$250.5384	$250.54	$250.55	$250.50
Purchase #6	$152.82	12.706%	$172.2373	$172.24	$172.25	$172.20
Purchase #7	$184.32	11.732%	$205.9444	$205.94	$205.95	$205.90
7 purchase totals =	$1,131.74		$1,233.7614	$1,233.76	$1,233.75	$1,233.70