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	$98.41	11.566%	$109.7921	$109.79	$109.80	$109.80
Purchase #2	$242.56	6.534%	$258.4089	$258.41	$258.40	$258.40
Purchase #3	$90.27	5.119%	$94.8909	$94.89	$94.90	$94.90
Purchase #4	$199.64	5.561%	$210.742	$210.74	$210.75	$210.70
Purchase #5	$57.82	9.776%	$63.4725	$63.47	$63.45	$63.50
Purchase #6	$80.38	3.462%	$83.1628	$83.16	$83.15	$83.20
Purchase #7	$217.52	4.150%	$226.5471	$226.55	$226.55	$226.50
7 purchase totals =	$986.60		$1,047.0163	$1,047.01	$1,047.00	$1,047.00