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	$135.69	5.126%	$142.6455	$142.65	$142.65	$142.60
Purchase #2	$78.91	5.578%	$83.3116	$83.31	$83.30	$83.30
Purchase #3	$161.90	12.740%	$182.5261	$182.53	$182.55	$182.50
Purchase #4	$123.91	10.766%	$137.2502	$137.25	$137.25	$137.30
Purchase #5	$119.54	11.688%	$133.5118	$133.51	$133.50	$133.50
Purchase #6	$222.74	5.577%	$235.1622	$235.16	$235.15	$235.20
Purchase #7	$127.33	10.334%	$140.4883	$140.49	$140.50	$140.50
7 purchase totals =	$970.02		$1,054.8957	$1,054.90	$1,054.90	$1,054.90