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	$116.75	12.163%	$130.9503	$130.95	$130.95	$131.00
Purchase #2	$198.33	10.660%	$219.472	$219.47	$219.45	$219.50
Purchase #3	$140.32	11.124%	$155.9292	$155.93	$155.95	$155.90
Purchase #4	$215.59	13.753%	$245.2401	$245.24	$245.25	$245.20
Purchase #5	$223.30	5.808%	$236.2693	$236.27	$236.25	$236.30
Purchase #6	$41.60	4.268%	$43.3755	$43.38	$43.40	$43.40
Purchase #7	$178.98	6.462%	$190.5457	$190.55	$190.55	$190.50
7 purchase totals =	$1,114.87		$1,221.7821	$1,221.79	$1,221.80	$1,221.80