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	$42.32	3.791%	$43.9244	$43.92	$43.90	$43.90
Purchase #2	$110.76	5.319%	$116.6513	$116.65	$116.65	$116.70
Purchase #3	$237.56	8.546%	$257.8619	$257.86	$257.85	$257.90
Purchase #4	$179.51	10.733%	$198.7768	$198.78	$198.80	$198.80
Purchase #5	$236.96	12.124%	$265.689	$265.69	$265.70	$265.70
Purchase #6	$41.44	6.526%	$44.1444	$44.14	$44.15	$44.10
Purchase #7	$204.90	9.192%	$223.7344	$223.73	$223.75	$223.70
7 purchase totals =	$1,053.45		$1,150.7822	$1,150.77	$1,150.80	$1,150.80