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	$78.37	9.113%	$85.5119	$85.51	$85.50	$85.50
Purchase #2	$81.79	12.551%	$92.0555	$92.06	$92.05	$92.10
Purchase #3	$152.41	6.566%	$162.4172	$162.42	$162.40	$162.40
Purchase #4	$112.86	12.588%	$127.0668	$127.07	$127.05	$127.10
Purchase #5	$203.43	10.333%	$224.4504	$224.45	$224.45	$224.50
Purchase #6	$139.41	5.795%	$147.4888	$147.49	$147.50	$147.50
Purchase #7	$168.44	13.354%	$190.9335	$190.93	$190.95	$190.90
7 purchase totals =	$936.71		$1,029.9241	$1,029.93	$1,029.90	$1,030.00