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	$178.34	11.564%	$198.9632	$198.96	$198.95	$199.00
Purchase #2	$82.83	6.207%	$87.9713	$87.97	$87.95	$88.00
Purchase #3	$169.61	5.142%	$178.3313	$178.33	$178.35	$178.30
Purchase #4	$138.42	5.802%	$146.4511	$146.45	$146.45	$146.50
Purchase #5	$247.95	5.151%	$260.7219	$260.72	$260.70	$260.70
Purchase #6	$34.35	9.709%	$37.685	$37.69	$37.70	$37.70
Purchase #7	$155.67	10.146%	$171.4643	$171.46	$171.45	$171.50
7 purchase totals =	$1,007.17		$1,081.5881	$1,081.58	$1,081.55	$1,081.70