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	$123.46	7.639%	$132.8911	$132.89	$132.90	$132.90
Purchase #2	$137.46	3.645%	$142.4704	$142.47	$142.45	$142.50
Purchase #3	$247.34	4.144%	$257.5898	$257.59	$257.60	$257.60
Purchase #4	$68.39	5.135%	$71.9018	$71.90	$71.90	$71.90
Purchase #5	$191.40	3.689%	$198.4607	$198.46	$198.45	$198.50
Purchase #6	$81.28	12.105%	$91.1189	$91.12	$91.10	$91.10
Purchase #7	$156.51	6.591%	$166.8256	$166.83	$166.85	$166.80
7 purchase totals =	$1,005.84		$1,061.2583	$1,061.26	$1,061.25	$1,061.30