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	$212.37	4.544%	$222.0201	$222.02	$222.00	$222.00
Purchase #2	$226.80	6.665%	$241.9162	$241.92	$241.90	$241.90
Purchase #3	$141.28	10.822%	$156.5693	$156.57	$156.55	$156.60
Purchase #4	$157.95	4.735%	$165.4289	$165.43	$165.45	$165.40
Purchase #5	$76.40	5.676%	$80.7365	$80.74	$80.75	$80.70
Purchase #6	$213.85	12.597%	$240.7887	$240.79	$240.80	$240.80
Purchase #7	$80.62	6.839%	$86.1336	$86.13	$86.15	$86.10
7 purchase totals =	$1,109.27		$1,193.5933	$1,193.60	$1,193.60	$1,193.50