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	$208.83	6.812%	$223.0555	$223.06	$223.05	$223.10
Purchase #2	$126.30	13.672%	$143.5677	$143.57	$143.55	$143.60
Purchase #3	$42.90	5.448%	$45.2372	$45.24	$45.25	$45.20
Purchase #4	$169.72	7.694%	$182.7783	$182.78	$182.80	$182.80
Purchase #5	$52.79	13.511%	$59.9225	$59.92	$59.90	$59.90
Purchase #6	$177.89	5.595%	$187.8429	$187.84	$187.85	$187.80
Purchase #7	$10.37	13.326%	$11.7519	$11.75	$11.75	$11.80
7 purchase totals =	$788.80		$854.1560	$854.16	$854.15	$854.20