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	$43.90	5.646%	$46.3786	$46.38	$46.40	$46.40
Purchase #2	$206.32	8.531%	$223.9212	$223.92	$223.90	$223.90
Purchase #3	$213.54	6.676%	$227.7959	$227.80	$227.80	$227.80
Purchase #4	$222.45	8.746%	$241.9055	$241.91	$241.90	$241.90
Purchase #5	$28.82	13.541%	$32.7225	$32.72	$32.70	$32.70
Purchase #6	$156.84	7.383%	$168.4195	$168.42	$168.40	$168.40
Purchase #7	$222.79	11.193%	$247.7269	$247.73	$247.75	$247.70
7 purchase totals =	$1,094.66		$1,188.8701	$1,188.88	$1,188.85	$1,188.80