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	$245.90	9.605%	$269.5187	$269.52	$269.50	$269.50
Purchase #2	$164.37	8.580%	$178.4729	$178.47	$178.45	$178.50
Purchase #3	$34.54	5.266%	$36.3589	$36.36	$36.35	$36.40
Purchase #4	$229.27	3.165%	$236.5264	$236.53	$236.55	$236.50
Purchase #5	$90.86	9.838%	$99.7988	$99.80	$99.80	$99.80
Purchase #6	$115.78	9.733%	$127.0489	$127.05	$127.05	$127.00
Purchase #7	$178.32	10.362%	$196.7975	$196.80	$196.80	$196.80
7 purchase totals =	$1,059.04		$1,144.5221	$1,144.53	$1,144.50	$1,144.50