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	$107.60	4.531%	$112.4754	$112.48	$112.50	$112.50
Purchase #2	$139.48	3.630%	$144.5431	$144.54	$144.55	$144.50
Purchase #3	$204.39	3.712%	$211.977	$211.98	$212.00	$212.00
Purchase #4	$95.72	7.357%	$102.7621	$102.76	$102.75	$102.80
Purchase #5	$79.86	11.563%	$89.0942	$89.09	$89.10	$89.10
Purchase #6	$215.91	3.848%	$224.2182	$224.22	$224.20	$224.20
Purchase #7	$124.33	7.455%	$133.5988	$133.60	$133.60	$133.60
7 purchase totals =	$967.29		$1,018.6688	$1,018.67	$1,018.70	$1,018.70