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	$177.84	4.533%	$185.9015	$185.90	$185.90	$185.90
Purchase #2	$13.93	3.749%	$14.4522	$14.45	$14.45	$14.50
Purchase #3	$232.55	10.123%	$256.091	$256.09	$256.10	$256.10
Purchase #4	$67.93	7.208%	$72.8264	$72.83	$72.85	$72.80
Purchase #5	$177.93	9.702%	$195.1928	$195.19	$195.20	$195.20
Purchase #6	$100.27	9.515%	$109.8107	$109.81	$109.80	$109.80
Purchase #7	$140.98	9.167%	$153.9036	$153.90	$153.90	$153.90
7 purchase totals =	$911.43		$988.1782	$988.17	$988.20	$988.20