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	$103.77	9.868%	$114.01	$114.01	$114.00	$114.00
Purchase #2	$35.90	9.485%	$39.3051	$39.31	$39.30	$39.30
Purchase #3	$34.33	12.324%	$38.5608	$38.56	$38.55	$38.60
Purchase #4	$50.49	12.670%	$56.8871	$56.89	$56.90	$56.90
Purchase #5	$185.43	10.337%	$204.5979	$204.60	$204.60	$204.60
Purchase #6	$66.38	11.435%	$73.9706	$73.97	$73.95	$74.00
Purchase #7	$124.46	12.601%	$140.1432	$140.14	$140.15	$140.10
7 purchase totals =	$600.76		$667.4747	$667.48	$667.45	$667.50