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	$164.54	9.172%	$179.6316	$179.63	$179.65	$179.60
Purchase #2	$63.92	6.188%	$67.8754	$67.88	$67.90	$67.90
Purchase #3	$226.84	4.264%	$236.5125	$236.51	$236.50	$236.50
Purchase #4	$130.26	9.422%	$142.5331	$142.53	$142.55	$142.50
Purchase #5	$181.52	4.405%	$189.516	$189.52	$189.50	$189.50
Purchase #6	$212.34	6.841%	$226.8662	$226.87	$226.85	$226.90
Purchase #7	$50.49	8.387%	$54.7246	$54.72	$54.70	$54.70
7 purchase totals =	$1,029.91		$1,097.6594	$1,097.66	$1,097.65	$1,097.60