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	$75.88	7.175%	$81.3244	$81.32	$81.30	$81.30
Purchase #2	$202.93	7.372%	$217.89	$217.89	$217.90	$217.90
Purchase #3	$41.56	4.262%	$43.3313	$43.33	$43.35	$43.30
Purchase #4	$152.33	4.874%	$159.7546	$159.75	$159.75	$159.80
Purchase #5	$132.32	7.138%	$141.765	$141.77	$141.75	$141.80
Purchase #6	$239.25	4.546%	$250.1263	$250.13	$250.15	$250.10
Purchase #7	$108.58	7.714%	$116.9559	$116.96	$116.95	$117.00
7 purchase totals =	$952.85		$1,011.1475	$1,011.15	$1,011.15	$1,011.20