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	$41.69	4.708%	$43.6528	$43.65	$43.65	$43.70
Purchase #2	$77.44	6.598%	$82.5495	$82.55	$82.55	$82.50
Purchase #3	$225.87	3.521%	$233.8229	$233.82	$233.80	$233.80
Purchase #4	$40.96	11.580%	$45.7032	$45.70	$45.70	$45.70
Purchase #5	$6.71	11.277%	$7.4667	$7.47	$7.45	$7.50
Purchase #6	$246.85	9.595%	$270.5353	$270.54	$270.55	$270.50
Purchase #7	$46.97	5.212%	$49.4181	$49.42	$49.40	$49.40
7 purchase totals =	$686.49		$733.1485	$733.15	$733.10	$733.10