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	$133.41	7.423%	$143.313	$143.31	$143.30	$143.30
Purchase #2	$243.98	7.331%	$261.8662	$261.87	$261.85	$261.90
Purchase #3	$184.55	3.364%	$190.7583	$190.76	$190.75	$190.80
Purchase #4	$196.57	10.818%	$217.8349	$217.83	$217.85	$217.80
Purchase #5	$248.51	7.804%	$267.9037	$267.90	$267.90	$267.90
Purchase #6	$20.28	6.236%	$21.5447	$21.54	$21.55	$21.50
Purchase #7	$189.42	3.259%	$195.5932	$195.59	$195.60	$195.60
7 purchase totals =	$1,216.72		$1,298.8140	$1,298.80	$1,298.80	$1,298.80