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	$181.64	5.274%	$191.2197	$191.22	$191.20	$191.20
Purchase #2	$83.64	6.502%	$89.0783	$89.08	$89.10	$89.10
Purchase #3	$15.72	13.793%	$17.8883	$17.89	$17.90	$17.90
Purchase #4	$41.65	5.529%	$43.9528	$43.95	$43.95	$44.00
Purchase #5	$123.63	8.777%	$134.481	$134.48	$134.50	$134.50
Purchase #6	$126.87	11.342%	$141.2596	$141.26	$141.25	$141.30
Purchase #7	$123.76	12.564%	$139.3092	$139.31	$139.30	$139.30
7 purchase totals =	$696.91		$757.1889	$757.19	$757.20	$757.30