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	$72.95	13.639%	$82.8997	$82.90	$82.90	$82.90
Purchase #2	$40.59	4.853%	$42.5598	$42.56	$42.55	$42.60
Purchase #3	$157.42	6.430%	$167.5421	$167.54	$167.55	$167.50
Purchase #4	$213.72	6.509%	$227.631	$227.63	$227.65	$227.60
Purchase #5	$170.91	7.166%	$183.1574	$183.16	$183.15	$183.20
Purchase #6	$170.63	8.431%	$185.0158	$185.02	$185.00	$185.00
Purchase #7	$85.89	11.871%	$96.086	$96.09	$96.10	$96.10
7 purchase totals =	$912.11		$984.8918	$984.90	$984.90	$984.90