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	$92.99	12.812%	$104.9039	$104.90	$104.90	$104.90
Purchase #2	$83.86	8.119%	$90.6686	$90.67	$90.65	$90.70
Purchase #3	$62.64	13.355%	$71.0056	$71.01	$71.00	$71.00
Purchase #4	$51.71	3.563%	$53.5524	$53.55	$53.55	$53.60
Purchase #5	$91.90	8.861%	$100.0433	$100.04	$100.05	$100.00
Purchase #6	$115.75	6.298%	$123.0399	$123.04	$123.05	$123.00
Purchase #7	$67.65	9.285%	$73.9313	$73.93	$73.95	$73.90
7 purchase totals =	$566.50		$617.1450	$617.14	$617.15	$617.10