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	$207.38	7.519%	$222.9729	$222.97	$222.95	$223.00
Purchase #2	$35.52	12.724%	$40.0396	$40.04	$40.05	$40.00
Purchase #3	$84.67	6.262%	$89.972	$89.97	$89.95	$90.00
Purchase #4	$137.50	9.694%	$150.8293	$150.83	$150.85	$150.80
Purchase #5	$132.30	10.399%	$146.0579	$146.06	$146.05	$146.10
Purchase #6	$29.44	4.829%	$30.8617	$30.86	$30.85	$30.90
Purchase #7	$223.81	12.387%	$251.5333	$251.53	$251.55	$251.50
7 purchase totals =	$850.62		$932.2667	$932.26	$932.25	$932.30