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	$99.59	4.779%	$104.3494	$104.35	$104.35	$104.30
Purchase #2	$145.76	8.334%	$157.9076	$157.91	$157.90	$157.90
Purchase #3	$190.44	3.380%	$196.8769	$196.88	$196.90	$196.90
Purchase #4	$171.50	3.550%	$177.5883	$177.59	$177.60	$177.60
Purchase #5	$137.95	10.376%	$152.2637	$152.26	$152.25	$152.30
Purchase #6	$99.44	5.681%	$105.0892	$105.09	$105.10	$105.10
Purchase #7	$185.28	10.734%	$205.168	$205.17	$205.15	$205.20
7 purchase totals =	$1,029.96		$1,099.2431	$1,099.25	$1,099.25	$1,099.30