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	$130.92	9.750%	$143.6847	$143.68	$143.70	$143.70
Purchase #2	$197.43	6.734%	$210.7249	$210.72	$210.70	$210.70
Purchase #3	$11.72	6.449%	$12.4758	$12.48	$12.50	$12.50
Purchase #4	$89.74	9.630%	$98.382	$98.38	$98.40	$98.40
Purchase #5	$108.86	8.631%	$118.2557	$118.26	$118.25	$118.30
Purchase #6	$90.67	13.475%	$102.8878	$102.89	$102.90	$102.90
Purchase #7	$39.94	5.560%	$42.1607	$42.16	$42.15	$42.20
7 purchase totals =	$669.28		$728.5716	$728.57	$728.60	$728.70