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	$145.31	5.815%	$153.7598	$153.76	$153.75	$153.80
Purchase #2	$52.37	4.128%	$54.5318	$54.53	$54.55	$54.50
Purchase #3	$139.41	8.234%	$150.889	$150.89	$150.90	$150.90
Purchase #4	$41.35	9.582%	$45.3122	$45.31	$45.30	$45.30
Purchase #5	$86.97	8.141%	$94.0502	$94.05	$94.05	$94.10
Purchase #6	$116.95	12.231%	$131.2542	$131.25	$131.25	$131.30
Purchase #7	$41.39	8.108%	$44.7459	$44.75	$44.75	$44.70
7 purchase totals =	$623.75		$674.5431	$674.54	$674.55	$674.60