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	$131.60	4.824%	$137.9484	$137.95	$137.95	$137.90
Purchase #2	$168.51	6.311%	$179.1447	$179.14	$179.15	$179.10
Purchase #3	$102.25	6.621%	$109.02	$109.02	$109.00	$109.00
Purchase #4	$231.39	9.423%	$253.1939	$253.19	$253.20	$253.20
Purchase #5	$103.29	7.189%	$110.7155	$110.72	$110.70	$110.70
Purchase #6	$128.90	12.431%	$144.9236	$144.92	$144.90	$144.90
Purchase #7	$178.84	4.333%	$186.5891	$186.59	$186.60	$186.60
7 purchase totals =	$1,044.78		$1,121.5352	$1,121.53	$1,121.50	$1,121.40