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	$49.98	7.653%	$53.805	$53.81	$53.80	$53.80
Purchase #2	$28.74	5.320%	$30.269	$30.27	$30.25	$30.30
Purchase #3	$130.58	7.213%	$139.9987	$140.00	$140.00	$140.00
Purchase #4	$124.49	5.318%	$131.1104	$131.11	$131.10	$131.10
Purchase #5	$232.50	11.284%	$258.7353	$258.74	$258.75	$258.70
Purchase #6	$213.43	4.156%	$222.3002	$222.30	$222.30	$222.30
Purchase #7	$101.29	9.859%	$111.2762	$111.28	$111.30	$111.30
7 purchase totals =	$881.01		$947.4948	$947.51	$947.50	$947.50