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	$68.72	5.582%	$72.556	$72.56	$72.55	$72.60
Purchase #2	$97.84	5.710%	$103.4267	$103.43	$103.45	$103.40
Purchase #3	$18.90	12.676%	$21.2958	$21.30	$21.30	$21.30
Purchase #4	$94.72	5.510%	$99.9391	$99.94	$99.95	$99.90
Purchase #5	$202.97	11.305%	$225.9158	$225.92	$225.90	$225.90
Purchase #6	$10.48	8.347%	$11.3548	$11.35	$11.35	$11.40
Purchase #7	$202.86	8.470%	$220.0422	$220.04	$220.05	$220.00
7 purchase totals =	$696.49		$754.5304	$754.54	$754.55	$754.50