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	$191.62	3.581%	$198.4819	$198.48	$198.50	$198.50
Purchase #2	$96.55	7.243%	$103.5431	$103.54	$103.55	$103.50
Purchase #3	$237.85	8.471%	$257.9983	$258.00	$258.00	$258.00
Purchase #4	$139.47	11.553%	$155.583	$155.58	$155.60	$155.60
Purchase #5	$36.75	9.495%	$40.2394	$40.24	$40.25	$40.20
Purchase #6	$37.62	9.869%	$41.3327	$41.33	$41.35	$41.30
Purchase #7	$141.81	7.619%	$152.6145	$152.61	$152.60	$152.60
7 purchase totals =	$881.67		$949.7929	$949.78	$949.85	$949.70