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	$200.77	12.345%	$225.5551	$225.56	$225.55	$225.60
Purchase #2	$215.34	12.341%	$241.9151	$241.92	$241.90	$241.90
Purchase #3	$186.99	11.467%	$208.4321	$208.43	$208.45	$208.40
Purchase #4	$58.89	6.366%	$62.6389	$62.64	$62.65	$62.60
Purchase #5	$19.35	6.831%	$20.6718	$20.67	$20.65	$20.70
Purchase #6	$175.32	7.734%	$188.8792	$188.88	$188.90	$188.90
Purchase #7	$180.31	3.119%	$185.9339	$185.93	$185.95	$185.90
7 purchase totals =	$1,036.97		$1,134.0261	$1,134.03	$1,134.05	$1,134.00