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	$111.25	4.837%	$116.6312	$116.63	$116.65	$116.60
Purchase #2	$143.48	6.206%	$152.3844	$152.38	$152.40	$152.40
Purchase #3	$117.73	9.426%	$128.8272	$128.83	$128.85	$128.80
Purchase #4	$27.65	12.139%	$31.0064	$31.01	$31.00	$31.00
Purchase #5	$180.63	4.852%	$189.3942	$189.39	$189.40	$189.40
Purchase #6	$110.71	11.142%	$123.0453	$123.05	$123.05	$123.00
Purchase #7	$40.41	4.293%	$42.1448	$42.14	$42.15	$42.10
7 purchase totals =	$731.86		$783.4335	$783.43	$783.50	$783.30