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	$101.55	11.701%	$113.4324	$113.43	$113.45	$113.40
Purchase #2	$136.90	5.856%	$144.9169	$144.92	$144.90	$144.90
Purchase #3	$165.38	5.592%	$174.628	$174.63	$174.65	$174.60
Purchase #4	$193.57	8.221%	$209.4834	$209.48	$209.50	$209.50
Purchase #5	$99.89	6.806%	$106.6885	$106.69	$106.70	$106.70
Purchase #6	$248.31	4.652%	$259.8614	$259.86	$259.85	$259.90
Purchase #7	$32.97	13.583%	$37.4483	$37.45	$37.45	$37.40
7 purchase totals =	$978.57		$1,046.4589	$1,046.46	$1,046.50	$1,046.40