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	$21.65	3.461%	$22.3993	$22.40	$22.40	$22.40
Purchase #2	$78.85	5.370%	$83.0842	$83.08	$83.10	$83.10
Purchase #3	$171.80	11.454%	$191.478	$191.48	$191.50	$191.50
Purchase #4	$98.44	5.332%	$103.6888	$103.69	$103.70	$103.70
Purchase #5	$213.81	9.358%	$233.8183	$233.82	$233.80	$233.80
Purchase #6	$87.59	4.528%	$91.5561	$91.56	$91.55	$91.60
Purchase #7	$98.79	6.462%	$105.1738	$105.17	$105.15	$105.20
7 purchase totals =	$770.93		$831.1985	$831.20	$831.20	$831.30