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	$66.45	3.541%	$68.803	$68.80	$68.80	$68.80
Purchase #2	$59.35	4.828%	$62.2154	$62.22	$62.20	$62.20
Purchase #3	$198.79	4.264%	$207.2664	$207.27	$207.25	$207.30
Purchase #4	$157.42	9.200%	$171.9026	$171.90	$171.90	$171.90
Purchase #5	$105.28	12.182%	$118.1052	$118.11	$118.10	$118.10
Purchase #6	$181.46	8.487%	$196.8605	$196.86	$196.85	$196.90
Purchase #7	$38.98	9.606%	$42.7244	$42.72	$42.70	$42.70
7 purchase totals =	$807.73		$867.8775	$867.88	$867.80	$867.90