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	$165.85	6.164%	$176.073	$176.07	$176.05	$176.10
Purchase #2	$142.89	13.320%	$161.9229	$161.92	$161.90	$161.90
Purchase #3	$90.95	3.373%	$94.0177	$94.02	$94.00	$94.00
Purchase #4	$29.80	12.178%	$33.429	$33.43	$33.45	$33.40
Purchase #5	$202.88	13.811%	$230.8998	$230.90	$230.90	$230.90
Purchase #6	$48.73	12.803%	$54.9689	$54.97	$54.95	$55.00
Purchase #7	$234.94	12.858%	$265.1486	$265.15	$265.15	$265.10
7 purchase totals =	$916.04		$1,016.4599	$1,016.46	$1,016.40	$1,016.40