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	$92.40	4.473%	$96.5331	$96.53	$96.55	$96.50
Purchase #2	$104.56	9.337%	$114.3228	$114.32	$114.30	$114.30
Purchase #3	$80.86	7.367%	$86.817	$86.82	$86.80	$86.80
Purchase #4	$164.46	9.222%	$179.6265	$179.63	$179.65	$179.60
Purchase #5	$193.87	9.847%	$212.9604	$212.96	$212.95	$213.00
Purchase #6	$119.40	3.702%	$123.8202	$123.82	$123.80	$123.80
Purchase #7	$38.46	10.382%	$42.4529	$42.45	$42.45	$42.50
7 purchase totals =	$794.01		$856.5329	$856.53	$856.50	$856.50