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	$51.94	13.654%	$59.0319	$59.03	$59.05	$59.00
Purchase #2	$138.38	13.263%	$156.7333	$156.73	$156.75	$156.70
Purchase #3	$30.87	12.770%	$34.8121	$34.81	$34.80	$34.80
Purchase #4	$63.77	13.845%	$72.599	$72.60	$72.60	$72.60
Purchase #5	$37.47	8.419%	$40.6246	$40.62	$40.60	$40.60
Purchase #6	$234.72	12.425%	$263.884	$263.88	$263.90	$263.90
Purchase #7	$78.50	13.778%	$89.3157	$89.32	$89.30	$89.30
7 purchase totals =	$635.65		$717.0006	$716.99	$717.00	$716.90