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	$116.78	6.144%	$123.955	$123.96	$123.95	$124.00
Purchase #2	$139.31	11.439%	$155.2457	$155.25	$155.25	$155.20
Purchase #3	$84.94	7.592%	$91.3886	$91.39	$91.40	$91.40
Purchase #4	$119.77	7.695%	$128.9863	$128.99	$129.00	$129.00
Purchase #5	$166.49	3.235%	$171.876	$171.88	$171.90	$171.90
Purchase #6	$153.37	13.861%	$174.6286	$174.63	$174.65	$174.60
Purchase #7	$247.54	4.772%	$259.3526	$259.35	$259.35	$259.40
7 purchase totals =	$1,028.20		$1,105.4328	$1,105.45	$1,105.50	$1,105.50