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	$146.32	4.243%	$152.5284	$152.53	$152.55	$152.50
Purchase #2	$35.95	8.524%	$39.0144	$39.01	$39.00	$39.00
Purchase #3	$119.78	9.279%	$130.8944	$130.89	$130.90	$130.90
Purchase #4	$35.84	7.517%	$38.5341	$38.53	$38.55	$38.50
Purchase #5	$130.47	7.125%	$139.766	$139.77	$139.75	$139.80
Purchase #6	$45.68	4.835%	$47.8886	$47.89	$47.90	$47.90
Purchase #7	$156.68	12.181%	$175.7652	$175.77	$175.75	$175.80
7 purchase totals =	$670.72		$724.3911	$724.39	$724.40	$724.40