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	$91.96	5.704%	$97.2054	$97.21	$97.20	$97.20
Purchase #2	$138.99	11.177%	$154.5249	$154.52	$154.50	$154.50
Purchase #3	$102.88	8.789%	$111.9221	$111.92	$111.90	$111.90
Purchase #4	$233.81	4.299%	$243.8615	$243.86	$243.85	$243.90
Purchase #5	$68.57	6.197%	$72.8193	$72.82	$72.80	$72.80
Purchase #6	$225.27	6.368%	$239.6152	$239.62	$239.60	$239.60
Purchase #7	$91.85	12.174%	$103.0318	$103.03	$103.05	$103.00
7 purchase totals =	$953.33		$1,022.9802	$1,022.98	$1,022.90	$1,022.90