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	$225.28	4.180%	$234.6967	$234.70	$234.70	$234.70
Purchase #2	$95.81	5.394%	$100.978	$100.98	$101.00	$101.00
Purchase #3	$37.84	13.845%	$43.0789	$43.08	$43.10	$43.10
Purchase #4	$141.82	10.535%	$156.7607	$156.76	$156.75	$156.80
Purchase #5	$126.35	10.270%	$139.3261	$139.33	$139.35	$139.30
Purchase #6	$206.96	11.418%	$230.5907	$230.59	$230.60	$230.60
Purchase #7	$54.79	12.459%	$61.6163	$61.62	$61.60	$61.60
7 purchase totals =	$888.85		$967.0474	$967.06	$967.10	$967.10