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	$76.50	9.520%	$83.7828	$83.78	$83.80	$83.80
Purchase #2	$107.94	13.780%	$122.8141	$122.81	$122.80	$122.80
Purchase #3	$80.77	10.771%	$89.4697	$89.47	$89.45	$89.50
Purchase #4	$156.75	6.600%	$167.0955	$167.10	$167.10	$167.10
Purchase #5	$216.79	13.271%	$245.5602	$245.56	$245.55	$245.60
Purchase #6	$88.47	3.576%	$91.6337	$91.63	$91.65	$91.60
Purchase #7	$44.51	4.539%	$46.5303	$46.53	$46.55	$46.50
7 purchase totals =	$771.73		$846.8863	$846.88	$846.90	$846.90