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	$240.96	9.701%	$264.3355	$264.34	$264.35	$264.30
Purchase #2	$11.35	7.440%	$12.1944	$12.19	$12.20	$12.20
Purchase #3	$129.45	7.722%	$139.4461	$139.45	$139.45	$139.40
Purchase #4	$151.48	13.270%	$171.5814	$171.58	$171.60	$171.60
Purchase #5	$134.97	5.586%	$142.5094	$142.51	$142.50	$142.50
Purchase #6	$149.25	11.426%	$166.3033	$166.30	$166.30	$166.30
Purchase #7	$199.70	8.593%	$216.8602	$216.86	$216.85	$216.90
7 purchase totals =	$1,017.16		$1,113.2303	$1,113.23	$1,113.25	$1,113.20