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	$189.57	13.296%	$214.7752	$214.78	$214.80	$214.80
Purchase #2	$227.54	12.673%	$256.3761	$256.38	$256.40	$256.40
Purchase #3	$31.74	6.329%	$33.7488	$33.75	$33.75	$33.70
Purchase #4	$85.83	3.329%	$88.6873	$88.69	$88.70	$88.70
Purchase #5	$169.54	9.490%	$185.6293	$185.63	$185.65	$185.60
Purchase #6	$109.83	9.339%	$120.087	$120.09	$120.10	$120.10
Purchase #7	$241.56	3.330%	$249.6039	$249.60	$249.60	$249.60
7 purchase totals =	$1,055.61		$1,148.9076	$1,148.92	$1,149.00	$1,148.90