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	$189.93	3.572%	$196.7143	$196.71	$196.70	$196.70
Purchase #2	$179.93	13.538%	$204.2889	$204.29	$204.30	$204.30
Purchase #3	$233.58	6.818%	$249.5055	$249.51	$249.50	$249.50
Purchase #4	$226.50	8.271%	$245.2338	$245.23	$245.25	$245.20
Purchase #5	$224.84	8.296%	$243.4927	$243.49	$243.50	$243.50
Purchase #6	$68.97	4.732%	$72.2337	$72.23	$72.25	$72.20
Purchase #7	$48.32	8.858%	$52.6002	$52.60	$52.60	$52.60
7 purchase totals =	$1,172.07		$1,264.0691	$1,264.06	$1,264.10	$1,264.00