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	$131.29	3.764%	$136.2318	$136.23	$136.25	$136.20
Purchase #2	$6.50	12.452%	$7.3094	$7.31	$7.30	$7.30
Purchase #3	$96.47	5.847%	$102.1106	$102.11	$102.10	$102.10
Purchase #4	$34.74	9.323%	$37.9788	$37.98	$38.00	$38.00
Purchase #5	$204.41	11.745%	$228.418	$228.42	$228.40	$228.40
Purchase #6	$33.64	11.822%	$37.6169	$37.62	$37.60	$37.60
Purchase #7	$164.78	7.149%	$176.5601	$176.56	$176.55	$176.60
7 purchase totals =	$671.83		$726.2256	$726.23	$726.20	$726.20