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	$83.86	8.253%	$90.781	$90.78	$90.80	$90.80
Purchase #2	$30.42	3.132%	$31.3728	$31.37	$31.35	$31.40
Purchase #3	$171.43	5.660%	$181.1329	$181.13	$181.15	$181.10
Purchase #4	$97.97	11.514%	$109.2503	$109.25	$109.25	$109.30
Purchase #5	$78.91	5.106%	$82.9391	$82.94	$82.95	$82.90
Purchase #6	$63.55	8.598%	$69.014	$69.01	$69.00	$69.00
Purchase #7	$204.71	5.398%	$215.7602	$215.76	$215.75	$215.80
7 purchase totals =	$730.85		$780.2503	$780.24	$780.25	$780.30