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	$129.25	7.820%	$139.3574	$139.36	$139.35	$139.40
Purchase #2	$161.42	13.260%	$182.8243	$182.82	$182.80	$182.80
Purchase #3	$63.43	5.649%	$67.0132	$67.01	$67.00	$67.00
Purchase #4	$192.91	8.507%	$209.3209	$209.32	$209.30	$209.30
Purchase #5	$65.83	8.341%	$71.3209	$71.32	$71.30	$71.30
Purchase #6	$212.88	7.839%	$229.5677	$229.57	$229.55	$229.60
Purchase #7	$173.49	8.533%	$188.2939	$188.29	$188.30	$188.30
7 purchase totals =	$999.21		$1,087.6983	$1,087.69	$1,087.60	$1,087.70