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	$199.28	6.631%	$212.4943	$212.49	$212.50	$212.50
Purchase #2	$40.52	5.779%	$42.8617	$42.86	$42.85	$42.90
Purchase #3	$207.54	5.281%	$218.5002	$218.50	$218.50	$218.50
Purchase #4	$212.95	9.638%	$233.4741	$233.47	$233.45	$233.50
Purchase #5	$177.85	7.209%	$190.6712	$190.67	$190.65	$190.70
Purchase #6	$67.41	5.248%	$70.9477	$70.95	$70.95	$70.90
Purchase #7	$103.34	5.518%	$109.0423	$109.04	$109.05	$109.00
7 purchase totals =	$1,008.89		$1,077.9915	$1,077.98	$1,077.95	$1,078.00