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	$145.66	7.744%	$156.9399	$156.94	$156.95	$156.90
Purchase #2	$125.44	13.167%	$141.9567	$141.96	$141.95	$142.00
Purchase #3	$169.87	6.500%	$180.9116	$180.91	$180.90	$180.90
Purchase #4	$145.91	3.859%	$151.5407	$151.54	$151.55	$151.50
Purchase #5	$135.67	7.441%	$145.7652	$145.77	$145.75	$145.80
Purchase #6	$86.72	4.397%	$90.5331	$90.53	$90.55	$90.50
Purchase #7	$224.31	6.510%	$238.9126	$238.91	$238.90	$238.90
7 purchase totals =	$1,033.58		$1,106.5598	$1,106.56	$1,106.55	$1,106.50