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	$20.79	6.126%	$22.0636	$22.06	$22.05	$22.10
Purchase #2	$245.46	4.497%	$256.4983	$256.50	$256.50	$256.50
Purchase #3	$85.38	6.374%	$90.8221	$90.82	$90.80	$90.80
Purchase #4	$79.91	6.454%	$85.0674	$85.07	$85.05	$85.10
Purchase #5	$72.61	13.291%	$82.2606	$82.26	$82.25	$82.30
Purchase #6	$158.77	9.112%	$173.2371	$173.24	$173.25	$173.20
Purchase #7	$146.45	6.619%	$156.1435	$156.14	$156.15	$156.10
7 purchase totals =	$809.37		$866.0926	$866.09	$866.05	$866.10