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	$80.52	11.600%	$89.8603	$89.86	$89.85	$89.90
Purchase #2	$213.63	3.725%	$221.5877	$221.59	$221.60	$221.60
Purchase #3	$77.55	5.660%	$81.9393	$81.94	$81.95	$81.90
Purchase #4	$99.71	10.332%	$110.012	$110.01	$110.00	$110.00
Purchase #5	$73.37	5.836%	$77.6519	$77.65	$77.65	$77.70
Purchase #6	$21.85	11.672%	$24.4003	$24.40	$24.40	$24.40
Purchase #7	$167.96	6.367%	$178.654	$178.65	$178.65	$178.70
7 purchase totals =	$734.59		$784.1055	$784.10	$784.10	$784.20