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	$197.96	13.442%	$224.5698	$224.57	$224.55	$224.60
Purchase #2	$38.82	10.752%	$42.9939	$42.99	$43.00	$43.00
Purchase #3	$115.46	3.566%	$119.5773	$119.58	$119.60	$119.60
Purchase #4	$39.27	8.256%	$42.5121	$42.51	$42.50	$42.50
Purchase #5	$59.35	4.279%	$61.8896	$61.89	$61.90	$61.90
Purchase #6	$196.48	7.578%	$211.3693	$211.37	$211.35	$211.40
Purchase #7	$155.88	6.228%	$165.5882	$165.59	$165.60	$165.60
7 purchase totals =	$803.22		$868.5002	$868.50	$868.50	$868.60