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	$161.63	4.514%	$168.926	$168.93	$168.95	$168.90
Purchase #2	$131.39	6.590%	$140.0486	$140.05	$140.05	$140.00
Purchase #3	$139.69	7.385%	$150.0061	$150.01	$150.00	$150.00
Purchase #4	$104.49	6.711%	$111.5023	$111.50	$111.50	$111.50
Purchase #5	$13.62	11.235%	$15.1502	$15.15	$15.15	$15.20
Purchase #6	$181.27	4.332%	$189.1226	$189.12	$189.10	$189.10
Purchase #7	$157.91	5.636%	$166.8098	$166.81	$166.80	$166.80
7 purchase totals =	$890.00		$941.5656	$941.57	$941.55	$941.50