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	$59.34	3.573%	$61.4602	$61.46	$61.45	$61.50
Purchase #2	$75.78	9.274%	$82.8078	$82.81	$82.80	$82.80
Purchase #3	$158.92	10.348%	$175.365	$175.37	$175.35	$175.40
Purchase #4	$89.43	9.605%	$98.0198	$98.02	$98.00	$98.00
Purchase #5	$98.77	3.733%	$102.4571	$102.46	$102.45	$102.50
Purchase #6	$163.37	4.622%	$170.921	$170.92	$170.90	$170.90
Purchase #7	$91.47	7.488%	$98.3193	$98.32	$98.30	$98.30
7 purchase totals =	$737.08		$789.3502	$789.36	$789.25	$789.40