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	$38.89	4.566%	$40.6657	$40.67	$40.65	$40.70
Purchase #2	$90.85	6.506%	$96.7607	$96.76	$96.75	$96.80
Purchase #3	$246.46	5.113%	$259.0615	$259.06	$259.05	$259.10
Purchase #4	$157.31	3.288%	$162.4824	$162.48	$162.50	$162.50
Purchase #5	$46.47	12.516%	$52.2862	$52.29	$52.30	$52.30
Purchase #6	$212.82	5.536%	$224.6017	$224.60	$224.60	$224.60
Purchase #7	$94.91	6.688%	$101.2576	$101.26	$101.25	$101.30
7 purchase totals =	$887.71		$937.1158	$937.12	$937.10	$937.30