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	$13.83	5.667%	$14.6137	$14.61	$14.60	$14.60
Purchase #2	$150.88	8.847%	$164.2284	$164.23	$164.25	$164.20
Purchase #3	$129.53	10.382%	$142.9778	$142.98	$143.00	$143.00
Purchase #4	$131.44	11.705%	$146.8251	$146.83	$146.85	$146.80
Purchase #5	$183.43	6.331%	$195.043	$195.04	$195.05	$195.00
Purchase #6	$59.94	13.408%	$67.9768	$67.98	$68.00	$68.00
Purchase #7	$134.25	12.562%	$151.1145	$151.11	$151.10	$151.10
7 purchase totals =	$803.30		$882.7793	$882.78	$882.85	$882.70