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	$84.85	12.726%	$95.648	$95.65	$95.65	$95.60
Purchase #2	$236.74	13.723%	$269.2278	$269.23	$269.25	$269.20
Purchase #3	$56.58	6.847%	$60.454	$60.45	$60.45	$60.50
Purchase #4	$218.57	7.270%	$234.46	$234.46	$234.45	$234.50
Purchase #5	$249.51	13.231%	$282.5227	$282.52	$282.50	$282.50
Purchase #6	$34.41	12.171%	$38.598	$38.60	$38.60	$38.60
Purchase #7	$32.86	7.520%	$35.3311	$35.33	$35.35	$35.30
7 purchase totals =	$913.52		$1,016.2416	$1,016.24	$1,016.25	$1,016.20