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	$224.29	5.132%	$235.8006	$235.80	$235.80	$235.80
Purchase #2	$187.86	4.810%	$196.8961	$196.90	$196.90	$196.90
Purchase #3	$115.98	3.447%	$119.9778	$119.98	$120.00	$120.00
Purchase #4	$247.83	9.341%	$270.9798	$270.98	$271.00	$271.00
Purchase #5	$37.63	11.299%	$41.8818	$41.88	$41.90	$41.90
Purchase #6	$61.88	6.533%	$65.9226	$65.92	$65.90	$65.90
Purchase #7	$130.47	8.263%	$141.2507	$141.25	$141.25	$141.30
7 purchase totals =	$1,005.94		$1,072.7094	$1,072.71	$1,072.75	$1,072.80