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	$48.56	10.426%	$53.6229	$53.62	$53.60	$53.60
Purchase #2	$131.39	5.764%	$138.9633	$138.96	$138.95	$139.00
Purchase #3	$37.84	4.656%	$39.6018	$39.60	$39.60	$39.60
Purchase #4	$216.55	9.654%	$237.4557	$237.46	$237.45	$237.50
Purchase #5	$158.60	3.697%	$164.4634	$164.46	$164.45	$164.50
Purchase #6	$11.79	5.825%	$12.4768	$12.48	$12.50	$12.50
Purchase #7	$204.25	9.147%	$222.9327	$222.93	$222.95	$222.90
7 purchase totals =	$808.98		$869.5166	$869.51	$869.50	$869.60