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	$137.28	7.685%	$147.83	$147.83	$147.85	$147.80
Purchase #2	$159.69	3.234%	$164.8544	$164.85	$164.85	$164.90
Purchase #3	$10.93	7.698%	$11.7714	$11.77	$11.75	$11.80
Purchase #4	$162.88	3.741%	$168.9733	$168.97	$168.95	$169.00
Purchase #5	$9.55	12.782%	$10.7707	$10.77	$10.75	$10.80
Purchase #6	$54.60	12.747%	$61.5599	$61.56	$61.55	$61.60
Purchase #7	$115.59	3.618%	$119.772	$119.77	$119.75	$119.80
7 purchase totals =	$650.52		$685.5317	$685.52	$685.45	$685.70