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	$93.77	7.560%	$100.859	$100.86	$100.85	$100.90
Purchase #2	$159.81	12.271%	$179.4203	$179.42	$179.40	$179.40
Purchase #3	$184.47	9.854%	$202.6477	$202.65	$202.65	$202.60
Purchase #4	$21.79	9.241%	$23.8036	$23.80	$23.80	$23.80
Purchase #5	$125.70	6.485%	$133.8516	$133.85	$133.85	$133.90
Purchase #6	$200.78	9.501%	$219.8561	$219.86	$219.85	$219.90
Purchase #7	$142.99	9.362%	$156.3767	$156.38	$156.40	$156.40
7 purchase totals =	$929.31		$1,016.8150	$1,016.82	$1,016.80	$1,016.90