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	$155.50	4.639%	$162.7136	$162.71	$162.70	$162.70
Purchase #2	$166.57	7.426%	$178.9395	$178.94	$178.95	$178.90
Purchase #3	$63.32	6.767%	$67.6049	$67.60	$67.60	$67.60
Purchase #4	$168.78	3.776%	$175.1531	$175.15	$175.15	$175.20
Purchase #5	$206.93	3.760%	$214.7106	$214.71	$214.70	$214.70
Purchase #6	$85.71	4.219%	$89.3261	$89.33	$89.35	$89.30
Purchase #7	$98.87	13.748%	$112.4626	$112.46	$112.45	$112.50
7 purchase totals =	$945.68		$1,000.9104	$1,000.90	$1,000.90	$1,000.90