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	$153.33	9.818%	$168.3839	$168.38	$168.40	$168.40
Purchase #2	$105.99	12.694%	$119.4444	$119.44	$119.45	$119.40
Purchase #3	$146.53	3.344%	$151.43	$151.43	$151.45	$151.40
Purchase #4	$75.57	9.106%	$82.4514	$82.45	$82.45	$82.50
Purchase #5	$157.86	8.872%	$171.8653	$171.87	$171.85	$171.90
Purchase #6	$39.59	5.787%	$41.8811	$41.88	$41.90	$41.90
Purchase #7	$197.74	13.601%	$224.6346	$224.63	$224.65	$224.60
7 purchase totals =	$876.61		$960.0907	$960.08	$960.15	$960.10