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	$122.49	7.712%	$131.9364	$131.94	$131.95	$131.90
Purchase #2	$225.84	8.744%	$245.5874	$245.59	$245.60	$245.60
Purchase #3	$206.52	3.758%	$214.281	$214.28	$214.30	$214.30
Purchase #4	$154.43	12.304%	$173.4311	$173.43	$173.45	$173.40
Purchase #5	$136.38	7.362%	$146.4203	$146.42	$146.40	$146.40
Purchase #6	$80.44	7.299%	$86.3113	$86.31	$86.30	$86.30
Purchase #7	$94.46	7.527%	$101.57	$101.57	$101.55	$101.60
7 purchase totals =	$1,020.56		$1,099.5375	$1,099.54	$1,099.55	$1,099.50