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	$63.89	8.463%	$69.297	$69.30	$69.30	$69.30
Purchase #2	$186.36	5.567%	$196.7347	$196.73	$196.75	$196.70
Purchase #3	$111.54	10.712%	$123.4882	$123.49	$123.50	$123.50
Purchase #4	$102.70	11.819%	$114.8381	$114.84	$114.85	$114.80
Purchase #5	$243.91	3.260%	$251.8615	$251.86	$251.85	$251.90
Purchase #6	$164.60	9.828%	$180.7769	$180.78	$180.80	$180.80
Purchase #7	$130.60	6.265%	$138.7821	$138.78	$138.80	$138.80
7 purchase totals =	$1,003.60		$1,075.7785	$1,075.78	$1,075.85	$1,075.80