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	$222.72	3.543%	$230.611	$230.61	$230.60	$230.60
Purchase #2	$233.63	9.740%	$256.3856	$256.39	$256.40	$256.40
Purchase #3	$28.53	3.789%	$29.611	$29.61	$29.60	$29.60
Purchase #4	$120.90	13.597%	$137.3388	$137.34	$137.35	$137.30
Purchase #5	$26.53	7.674%	$28.5659	$28.57	$28.55	$28.60
Purchase #6	$187.78	6.129%	$199.289	$199.29	$199.30	$199.30
Purchase #7	$179.76	4.365%	$187.6065	$187.61	$187.60	$187.60
7 purchase totals =	$999.85		$1,069.4078	$1,069.42	$1,069.40	$1,069.40