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	$106.43	9.238%	$116.262	$116.26	$116.25	$116.30
Purchase #2	$98.53	6.646%	$105.0783	$105.08	$105.10	$105.10
Purchase #3	$235.33	4.376%	$245.628	$245.63	$245.65	$245.60
Purchase #4	$95.83	3.815%	$99.4859	$99.49	$99.50	$99.50
Purchase #5	$248.37	9.320%	$271.5181	$271.52	$271.50	$271.50
Purchase #6	$86.95	3.769%	$90.2271	$90.23	$90.25	$90.20
Purchase #7	$238.74	11.813%	$266.9424	$266.94	$266.95	$266.90
7 purchase totals =	$1,110.18		$1,195.1418	$1,195.15	$1,195.20	$1,195.10