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	$167.63	5.579%	$176.9821	$176.98	$177.00	$177.00
Purchase #2	$233.89	12.453%	$263.0163	$263.02	$263.00	$263.00
Purchase #3	$7.56	4.236%	$7.8802	$7.88	$7.90	$7.90
Purchase #4	$238.56	4.483%	$249.2546	$249.25	$249.25	$249.30
Purchase #5	$82.50	9.582%	$90.4052	$90.41	$90.40	$90.40
Purchase #6	$183.40	4.834%	$192.2656	$192.27	$192.25	$192.30
Purchase #7	$241.46	9.416%	$264.1959	$264.20	$264.20	$264.20
7 purchase totals =	$1,155.00		$1,243.9999	$1,244.01	$1,244.00	$1,244.10