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	$98.58	7.385%	$105.8601	$105.86	$105.85	$105.90
Purchase #2	$194.81	10.430%	$215.1287	$215.13	$215.15	$215.10
Purchase #3	$176.46	6.228%	$187.4499	$187.45	$187.45	$187.40
Purchase #4	$128.58	11.156%	$142.9244	$142.92	$142.90	$142.90
Purchase #5	$31.31	5.783%	$33.1207	$33.12	$33.10	$33.10
Purchase #6	$163.54	4.624%	$171.1021	$171.10	$171.10	$171.10
Purchase #7	$46.57	7.869%	$50.2346	$50.23	$50.25	$50.20
7 purchase totals =	$839.85		$905.8205	$905.81	$905.80	$905.70