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	$250.39	10.567%	$276.8487	$276.85	$276.85	$276.80
Purchase #2	$133.38	5.528%	$140.7532	$140.75	$140.75	$140.80
Purchase #3	$144.53	3.791%	$150.0091	$150.01	$150.00	$150.00
Purchase #4	$249.83	4.232%	$260.4028	$260.40	$260.40	$260.40
Purchase #5	$215.86	9.251%	$235.8292	$235.83	$235.85	$235.80
Purchase #6	$109.43	7.867%	$118.0389	$118.04	$118.05	$118.00
Purchase #7	$104.30	13.802%	$118.6955	$118.70	$118.70	$118.70
7 purchase totals =	$1,207.72		$1,300.5774	$1,300.58	$1,300.60	$1,300.50