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	$185.44	7.582%	$199.5001	$199.50	$199.50	$199.50
Purchase #2	$35.78	3.219%	$36.9318	$36.93	$36.95	$36.90
Purchase #3	$48.73	8.508%	$52.8759	$52.88	$52.90	$52.90
Purchase #4	$152.84	10.113%	$168.2967	$168.30	$168.30	$168.30
Purchase #5	$156.82	7.238%	$168.1706	$168.17	$168.15	$168.20
Purchase #6	$163.77	10.195%	$180.4664	$180.47	$180.45	$180.50
Purchase #7	$165.25	13.119%	$186.9291	$186.93	$186.95	$186.90
7 purchase totals =	$908.63		$993.1706	$993.18	$993.20	$993.20