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	$190.38	4.144%	$198.2693	$198.27	$198.25	$198.30
Purchase #2	$90.59	9.164%	$98.8917	$98.89	$98.90	$98.90
Purchase #3	$102.91	10.833%	$114.0582	$114.06	$114.05	$114.10
Purchase #4	$170.53	3.222%	$176.0245	$176.02	$176.00	$176.00
Purchase #5	$154.88	11.682%	$172.9731	$172.97	$172.95	$173.00
Purchase #6	$126.90	8.122%	$137.2068	$137.21	$137.20	$137.20
Purchase #7	$10.75	10.696%	$11.8998	$11.90	$11.90	$11.90
7 purchase totals =	$846.94		$909.3234	$909.32	$909.25	$909.40