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	$144.25	9.546%	$158.0201	$158.02	$158.00	$158.00
Purchase #2	$86.61	12.500%	$97.4363	$97.44	$97.45	$97.40
Purchase #3	$240.51	3.558%	$249.0673	$249.07	$249.05	$249.10
Purchase #4	$144.64	13.703%	$164.46	$164.46	$164.45	$164.50
Purchase #5	$139.71	9.142%	$152.4823	$152.48	$152.50	$152.50
Purchase #6	$151.74	7.542%	$163.1842	$163.18	$163.20	$163.20
Purchase #7	$74.40	11.179%	$82.7172	$82.72	$82.70	$82.70
7 purchase totals =	$981.86		$1,067.3674	$1,067.37	$1,067.35	$1,067.40