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	$72.72	13.450%	$82.5008	$82.50	$82.50	$82.50
Purchase #2	$14.36	9.337%	$15.7008	$15.70	$15.70	$15.70
Purchase #3	$141.52	10.334%	$156.1447	$156.14	$156.15	$156.10
Purchase #4	$178.91	8.513%	$194.1406	$194.14	$194.15	$194.10
Purchase #5	$75.75	13.513%	$85.9861	$85.99	$86.00	$86.00
Purchase #6	$211.42	11.399%	$235.5198	$235.52	$235.50	$235.50
Purchase #7	$33.67	11.686%	$37.6047	$37.60	$37.60	$37.60
7 purchase totals =	$728.35		$807.5975	$807.59	$807.60	$807.50