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	$161.48	6.526%	$172.0182	$172.02	$172.00	$172.00
Purchase #2	$74.54	9.201%	$81.3984	$81.40	$81.40	$81.40
Purchase #3	$60.45	7.845%	$65.1923	$65.19	$65.20	$65.20
Purchase #4	$61.39	9.508%	$67.227	$67.23	$67.25	$67.20
Purchase #5	$40.69	8.515%	$44.1548	$44.15	$44.15	$44.20
Purchase #6	$196.38	6.245%	$208.6439	$208.64	$208.65	$208.60
Purchase #7	$120.83	9.123%	$131.8533	$131.85	$131.85	$131.90
7 purchase totals =	$715.76		$770.4879	$770.48	$770.50	$770.50