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	$98.91	4.626%	$103.4856	$103.49	$103.50	$103.50
Purchase #2	$234.36	4.811%	$245.6351	$245.64	$245.65	$245.60
Purchase #3	$8.27	8.210%	$8.949	$8.95	$8.95	$8.90
Purchase #4	$94.47	9.695%	$103.6289	$103.63	$103.65	$103.60
Purchase #5	$86.93	3.350%	$89.8422	$89.84	$89.85	$89.80
Purchase #6	$64.40	12.480%	$72.4371	$72.44	$72.45	$72.40
Purchase #7	$29.53	5.733%	$31.223	$31.22	$31.20	$31.20
7 purchase totals =	$616.87		$655.2009	$655.21	$655.25	$655.00