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	$176.79	7.417%	$189.9025	$189.90	$189.90	$189.90
Purchase #2	$134.60	5.161%	$141.5467	$141.55	$141.55	$141.50
Purchase #3	$133.93	8.419%	$145.2056	$145.21	$145.20	$145.20
Purchase #4	$207.27	9.649%	$227.2695	$227.27	$227.25	$227.30
Purchase #5	$95.62	10.736%	$105.8858	$105.89	$105.90	$105.90
Purchase #6	$28.26	9.310%	$30.891	$30.89	$30.90	$30.90
Purchase #7	$161.60	6.588%	$172.2462	$172.25	$172.25	$172.20
7 purchase totals =	$938.07		$1,012.9473	$1,012.96	$1,012.95	$1,012.90