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	$118.88	4.114%	$123.7707	$123.77	$123.75	$123.80
Purchase #2	$42.62	13.508%	$48.3771	$48.38	$48.40	$48.40
Purchase #3	$149.39	8.671%	$162.3436	$162.34	$162.35	$162.30
Purchase #4	$186.49	6.282%	$198.2053	$198.21	$198.20	$198.20
Purchase #5	$73.98	11.464%	$82.4611	$82.46	$82.45	$82.50
Purchase #6	$208.44	6.801%	$222.616	$222.62	$222.60	$222.60
Purchase #7	$41.77	8.291%	$45.2332	$45.23	$45.25	$45.20
7 purchase totals =	$821.57		$883.0070	$883.01	$883.00	$883.00