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	$106.93	10.209%	$117.8465	$117.85	$117.85	$117.80
Purchase #2	$35.67	13.324%	$40.4227	$40.42	$40.40	$40.40
Purchase #3	$183.54	13.461%	$208.2463	$208.25	$208.25	$208.20
Purchase #4	$207.87	5.301%	$218.8892	$218.89	$218.90	$218.90
Purchase #5	$244.71	10.429%	$270.2308	$270.23	$270.25	$270.20
Purchase #6	$54.64	7.770%	$58.8855	$58.89	$58.90	$58.90
Purchase #7	$84.69	13.260%	$95.9199	$95.92	$95.90	$95.90
7 purchase totals =	$918.05		$1,010.4409	$1,010.45	$1,010.45	$1,010.30