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	$124.58	5.670%	$131.6437	$131.64	$131.65	$131.60
Purchase #2	$132.34	8.696%	$143.8483	$143.85	$143.85	$143.80
Purchase #3	$226.54	11.839%	$253.3601	$253.36	$253.35	$253.40
Purchase #4	$224.85	3.789%	$233.3696	$233.37	$233.35	$233.40
Purchase #5	$99.55	5.113%	$104.64	$104.64	$104.65	$104.60
Purchase #6	$63.63	13.585%	$72.2741	$72.27	$72.25	$72.30
Purchase #7	$172.53	7.319%	$185.1575	$185.16	$185.15	$185.20
7 purchase totals =	$1,044.02		$1,124.2933	$1,124.29	$1,124.25	$1,124.30