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	$138.92	12.858%	$156.7823	$156.78	$156.80	$156.80
Purchase #2	$81.45	4.524%	$85.1348	$85.13	$85.15	$85.10
Purchase #3	$89.29	8.328%	$96.7261	$96.73	$96.75	$96.70
Purchase #4	$203.36	5.623%	$214.7949	$214.79	$214.80	$214.80
Purchase #5	$191.52	13.542%	$217.4556	$217.46	$217.45	$217.50
Purchase #6	$17.89	13.202%	$20.2518	$20.25	$20.25	$20.30
Purchase #7	$219.29	6.442%	$233.4167	$233.42	$233.40	$233.40
7 purchase totals =	$941.72		$1,024.5622	$1,024.56	$1,024.60	$1,024.60