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	$68.82	6.144%	$73.0483	$73.05	$73.05	$73.00
Purchase #2	$59.96	11.287%	$66.7277	$66.73	$66.75	$66.70
Purchase #3	$32.98	6.130%	$35.0017	$35.00	$35.00	$35.00
Purchase #4	$39.29	7.565%	$42.2623	$42.26	$42.25	$42.30
Purchase #5	$217.59	3.815%	$225.8911	$225.89	$225.90	$225.90
Purchase #6	$54.28	11.838%	$60.7057	$60.71	$60.70	$60.70
Purchase #7	$84.53	6.206%	$89.7759	$89.78	$89.80	$89.80
7 purchase totals =	$557.45		$593.4127	$593.42	$593.45	$593.40