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	$168.67	5.844%	$178.5271	$178.53	$178.55	$178.50
Purchase #2	$127.30	13.570%	$144.5746	$144.57	$144.55	$144.60
Purchase #3	$191.47	12.648%	$215.6871	$215.69	$215.70	$215.70
Purchase #4	$134.51	8.802%	$146.3496	$146.35	$146.35	$146.30
Purchase #5	$153.30	10.290%	$169.0746	$169.07	$169.05	$169.10
Purchase #6	$178.72	7.824%	$192.7031	$192.70	$192.70	$192.70
Purchase #7	$67.70	6.752%	$72.2711	$72.27	$72.25	$72.30
7 purchase totals =	$1,021.67		$1,119.1872	$1,119.18	$1,119.15	$1,119.20