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	$145.54	7.690%	$156.732	$156.73	$156.75	$156.70
Purchase #2	$249.67	8.750%	$271.5161	$271.52	$271.50	$271.50
Purchase #3	$100.65	10.504%	$111.2223	$111.22	$111.20	$111.20
Purchase #4	$200.57	4.705%	$210.0068	$210.01	$210.00	$210.00
Purchase #5	$210.27	7.444%	$225.9225	$225.92	$225.90	$225.90
Purchase #6	$246.46	9.691%	$270.3444	$270.34	$270.35	$270.30
Purchase #7	$106.80	7.241%	$114.5334	$114.53	$114.55	$114.50
7 purchase totals =	$1,259.96		$1,360.2775	$1,360.27	$1,360.25	$1,360.10