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	$61.44	13.622%	$69.8094	$69.81	$69.80	$69.80
Purchase #2	$42.37	7.117%	$45.3855	$45.39	$45.40	$45.40
Purchase #3	$157.61	9.539%	$172.6444	$172.64	$172.65	$172.60
Purchase #4	$199.65	10.748%	$221.1084	$221.11	$221.10	$221.10
Purchase #5	$245.99	7.239%	$263.7972	$263.80	$263.80	$263.80
Purchase #6	$105.97	8.348%	$114.8164	$114.82	$114.80	$114.80
Purchase #7	$213.90	4.473%	$223.4677	$223.47	$223.45	$223.50
7 purchase totals =	$1,026.93		$1,111.0290	$1,111.04	$1,111.00	$1,111.00