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	$153.96	11.537%	$171.7224	$171.72	$171.70	$171.70
Purchase #2	$133.64	7.543%	$143.7205	$143.72	$143.70	$143.70
Purchase #3	$143.82	6.756%	$153.5365	$153.54	$153.55	$153.50
Purchase #4	$140.41	12.747%	$158.3081	$158.31	$158.30	$158.30
Purchase #5	$72.49	10.197%	$79.8818	$79.88	$79.90	$79.90
Purchase #6	$228.71	13.528%	$259.6499	$259.65	$259.65	$259.60
Purchase #7	$46.74	6.706%	$49.8744	$49.87	$49.85	$49.90
7 purchase totals =	$919.77		$1,016.6936	$1,016.69	$1,016.65	$1,016.60