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	$174.59	9.319%	$190.86	$190.86	$190.85	$190.90
Purchase #2	$139.59	4.524%	$145.9051	$145.91	$145.90	$145.90
Purchase #3	$99.83	12.743%	$112.5513	$112.55	$112.55	$112.60
Purchase #4	$80.72	11.610%	$90.0916	$90.09	$90.10	$90.10
Purchase #5	$243.72	7.492%	$261.9795	$261.98	$262.00	$262.00
Purchase #6	$116.52	3.567%	$120.6763	$120.68	$120.70	$120.70
Purchase #7	$213.51	8.725%	$232.1387	$232.14	$232.15	$232.10
7 purchase totals =	$1,068.48		$1,154.2025	$1,154.21	$1,154.25	$1,154.30