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	$108.39	4.757%	$113.5461	$113.55	$113.55	$113.50
Purchase #2	$180.32	10.316%	$198.9218	$198.92	$198.90	$198.90
Purchase #3	$101.89	6.245%	$108.253	$108.25	$108.25	$108.30
Purchase #4	$10.39	13.627%	$11.8058	$11.81	$11.80	$11.80
Purchase #5	$145.49	10.327%	$160.5148	$160.51	$160.50	$160.50
Purchase #6	$113.43	7.869%	$122.3558	$122.36	$122.35	$122.40
Purchase #7	$85.63	4.469%	$89.4568	$89.46	$89.45	$89.50
7 purchase totals =	$745.54		$804.8541	$804.86	$804.80	$804.90