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	$152.62	9.450%	$167.0426	$167.04	$167.05	$167.00
Purchase #2	$28.36	9.373%	$31.0182	$31.02	$31.00	$31.00
Purchase #3	$133.96	8.523%	$145.3774	$145.38	$145.40	$145.40
Purchase #4	$106.56	11.653%	$118.9774	$118.98	$119.00	$119.00
Purchase #5	$145.26	13.572%	$164.9747	$164.97	$164.95	$165.00
Purchase #6	$234.55	6.754%	$250.3915	$250.39	$250.40	$250.40
Purchase #7	$78.98	13.273%	$89.463	$89.46	$89.45	$89.50
7 purchase totals =	$880.29		$967.2448	$967.24	$967.25	$967.30