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	$189.77	13.308%	$215.0246	$215.02	$215.00	$215.00
Purchase #2	$73.75	5.661%	$77.925	$77.93	$77.95	$77.90
Purchase #3	$112.93	3.258%	$116.6093	$116.61	$116.60	$116.60
Purchase #4	$38.93	6.160%	$41.3281	$41.33	$41.35	$41.30
Purchase #5	$37.60	8.850%	$40.9276	$40.93	$40.95	$40.90
Purchase #6	$227.97	4.681%	$238.6413	$238.64	$238.65	$238.60
Purchase #7	$242.79	11.670%	$271.1236	$271.12	$271.10	$271.10
7 purchase totals =	$923.74		$1,001.5795	$1,001.58	$1,001.60	$1,001.40