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	$84.42	7.363%	$90.6358	$90.64	$90.65	$90.60
Purchase #2	$84.69	10.462%	$93.5503	$93.55	$93.55	$93.60
Purchase #3	$35.94	5.622%	$37.9605	$37.96	$37.95	$38.00
Purchase #4	$204.59	7.682%	$220.3066	$220.31	$220.30	$220.30
Purchase #5	$85.75	6.684%	$91.4815	$91.48	$91.50	$91.50
Purchase #6	$12.89	13.160%	$14.5863	$14.59	$14.60	$14.60
Purchase #7	$180.97	5.407%	$190.755	$190.76	$190.75	$190.80
7 purchase totals =	$689.25		$739.2760	$739.29	$739.30	$739.40