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	$41.79	3.193%	$43.1244	$43.12	$43.10	$43.10
Purchase #2	$153.48	13.717%	$174.5329	$174.53	$174.55	$174.50
Purchase #3	$7.47	3.839%	$7.7568	$7.76	$7.75	$7.80
Purchase #4	$8.50	4.516%	$8.8839	$8.88	$8.90	$8.90
Purchase #5	$74.44	4.545%	$77.8233	$77.82	$77.80	$77.80
Purchase #6	$240.35	9.133%	$262.3012	$262.30	$262.30	$262.30
Purchase #7	$173.56	13.366%	$196.758	$196.76	$196.75	$196.80
7 purchase totals =	$699.59		$771.1805	$771.17	$771.15	$771.20