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	$43.38	11.353%	$48.3049	$48.30	$48.30	$48.30
Purchase #2	$211.73	4.192%	$220.6057	$220.61	$220.60	$220.60
Purchase #3	$134.85	7.189%	$144.5444	$144.54	$144.55	$144.50
Purchase #4	$185.95	7.646%	$200.1677	$200.17	$200.15	$200.20
Purchase #5	$142.38	7.183%	$152.6072	$152.61	$152.60	$152.60
Purchase #6	$154.79	12.783%	$174.5768	$174.58	$174.60	$174.60
Purchase #7	$52.89	7.226%	$56.7118	$56.71	$56.70	$56.70
7 purchase totals =	$925.97		$997.5185	$997.52	$997.50	$997.50