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	$103.81	9.563%	$113.7374	$113.74	$113.75	$113.70
Purchase #2	$214.99	10.524%	$237.6155	$237.62	$237.60	$237.60
Purchase #3	$212.91	4.618%	$222.7422	$222.74	$222.75	$222.70
Purchase #4	$126.30	10.616%	$139.708	$139.71	$139.70	$139.70
Purchase #5	$55.62	12.474%	$62.558	$62.56	$62.55	$62.60
Purchase #6	$150.37	11.454%	$167.5934	$167.59	$167.60	$167.60
Purchase #7	$160.82	4.748%	$168.4557	$168.46	$168.45	$168.50
7 purchase totals =	$1,024.82		$1,112.4102	$1,112.42	$1,112.40	$1,112.40