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	$72.97	13.478%	$82.8049	$82.80	$82.80	$82.80
Purchase #2	$19.26	5.611%	$20.3407	$20.34	$20.35	$20.30
Purchase #3	$114.98	7.477%	$123.5771	$123.58	$123.60	$123.60
Purchase #4	$244.65	7.413%	$262.7859	$262.79	$262.80	$262.80
Purchase #5	$217.52	12.752%	$245.2582	$245.26	$245.25	$245.30
Purchase #6	$63.60	11.610%	$70.984	$70.98	$71.00	$71.00
Purchase #7	$54.42	10.759%	$60.275	$60.28	$60.30	$60.30
7 purchase totals =	$787.40		$866.0258	$866.03	$866.10	$866.10