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	$206.43	4.328%	$215.3643	$215.36	$215.35	$215.40
Purchase #2	$103.41	5.520%	$109.1182	$109.12	$109.10	$109.10
Purchase #3	$88.82	12.637%	$100.0442	$100.04	$100.05	$100.00
Purchase #4	$120.32	13.745%	$136.858	$136.86	$136.85	$136.90
Purchase #5	$133.73	7.411%	$143.6407	$143.64	$143.65	$143.60
Purchase #6	$143.31	9.300%	$156.6378	$156.64	$156.65	$156.60
Purchase #7	$59.35	6.191%	$63.0244	$63.02	$63.00	$63.00
7 purchase totals =	$855.37		$924.6876	$924.68	$924.65	$924.60