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	$42.65	9.558%	$46.7265	$46.73	$46.75	$46.70
Purchase #2	$78.98	13.238%	$89.4354	$89.44	$89.45	$89.40
Purchase #3	$33.85	7.174%	$36.2784	$36.28	$36.30	$36.30
Purchase #4	$116.46	8.797%	$126.705	$126.71	$126.70	$126.70
Purchase #5	$29.47	13.290%	$33.3866	$33.39	$33.40	$33.40
Purchase #6	$227.31	5.410%	$239.6075	$239.61	$239.60	$239.60
Purchase #7	$139.43	11.843%	$155.9427	$155.94	$155.95	$155.90
7 purchase totals =	$668.15		$728.0821	$728.10	$728.15	$728.00