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	$60.42	8.853%	$65.769	$65.77	$65.75	$65.80
Purchase #2	$62.94	6.490%	$67.0248	$67.02	$67.00	$67.00
Purchase #3	$182.92	4.666%	$191.455	$191.46	$191.45	$191.50
Purchase #4	$34.39	3.213%	$35.495	$35.50	$35.50	$35.50
Purchase #5	$206.52	13.732%	$234.8793	$234.88	$234.90	$234.90
Purchase #6	$142.71	5.698%	$150.8416	$150.84	$150.85	$150.80
Purchase #7	$55.55	7.114%	$59.5018	$59.50	$59.50	$59.50
7 purchase totals =	$745.45		$804.9665	$804.97	$804.95	$805.00