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	$244.44	8.470%	$265.1441	$265.14	$265.15	$265.10
Purchase #2	$200.57	12.510%	$225.6613	$225.66	$225.65	$225.70
Purchase #3	$192.65	13.747%	$219.1336	$219.13	$219.15	$219.10
Purchase #4	$146.32	3.477%	$151.4075	$151.41	$151.40	$151.40
Purchase #5	$81.60	12.524%	$91.8196	$91.82	$91.80	$91.80
Purchase #6	$146.30	13.756%	$166.425	$166.43	$166.45	$166.40
Purchase #7	$104.94	13.359%	$118.9589	$118.96	$118.95	$119.00
7 purchase totals =	$1,116.82		$1,238.5500	$1,238.55	$1,238.55	$1,238.50