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	$199.79	4.150%	$208.0813	$208.08	$208.10	$208.10
Purchase #2	$79.48	8.569%	$86.2906	$86.29	$86.30	$86.30
Purchase #3	$39.40	5.518%	$41.5741	$41.57	$41.55	$41.60
Purchase #4	$158.89	8.816%	$172.8977	$172.90	$172.90	$172.90
Purchase #5	$39.39	11.245%	$43.8194	$43.82	$43.80	$43.80
Purchase #6	$205.25	6.732%	$219.0674	$219.07	$219.05	$219.10
Purchase #7	$237.54	13.370%	$269.2991	$269.30	$269.30	$269.30
7 purchase totals =	$959.74		$1,041.0296	$1,041.03	$1,041.00	$1,041.10