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	$161.47	8.767%	$175.6261	$175.63	$175.65	$175.60
Purchase #2	$70.85	10.740%	$78.4593	$78.46	$78.45	$78.50
Purchase #3	$7.32	3.552%	$7.58	$7.58	$7.60	$7.60
Purchase #4	$228.91	4.203%	$238.5311	$238.53	$238.55	$238.50
Purchase #5	$187.46	13.317%	$212.424	$212.42	$212.40	$212.40
Purchase #6	$78.66	9.824%	$86.3876	$86.39	$86.40	$86.40
Purchase #7	$182.43	9.750%	$200.2169	$200.22	$200.20	$200.20
7 purchase totals =	$917.10		$999.2250	$999.23	$999.25	$999.20