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	$102.95	5.759%	$108.8789	$108.88	$108.90	$108.90
Purchase #2	$171.37	7.284%	$183.8526	$183.85	$183.85	$183.90
Purchase #3	$88.49	8.236%	$95.778	$95.78	$95.80	$95.80
Purchase #4	$171.34	8.524%	$185.945	$185.95	$185.95	$185.90
Purchase #5	$107.85	12.559%	$121.3949	$121.39	$121.40	$121.40
Purchase #6	$250.88	9.402%	$274.4677	$274.47	$274.45	$274.50
Purchase #7	$37.50	4.389%	$39.1459	$39.15	$39.15	$39.10
7 purchase totals =	$930.38		$1,009.4630	$1,009.47	$1,009.50	$1,009.50