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	$189.77	4.739%	$198.7632	$198.76	$198.75	$198.80
Purchase #2	$52.83	3.672%	$54.7699	$54.77	$54.75	$54.80
Purchase #3	$6.60	11.217%	$7.3403	$7.34	$7.35	$7.30
Purchase #4	$88.33	7.778%	$95.2003	$95.20	$95.20	$95.20
Purchase #5	$144.74	5.867%	$153.2319	$153.23	$153.25	$153.20
Purchase #6	$151.55	10.417%	$167.337	$167.34	$167.35	$167.30
Purchase #7	$68.78	5.339%	$72.4522	$72.45	$72.45	$72.50
7 purchase totals =	$702.60		$749.0948	$749.09	$749.10	$749.10