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	$123.93	6.416%	$131.8813	$131.88	$131.90	$131.90
Purchase #2	$179.71	4.832%	$188.3936	$188.39	$188.40	$188.40
Purchase #3	$93.89	10.257%	$103.5203	$103.52	$103.50	$103.50
Purchase #4	$31.45	5.768%	$33.264	$33.26	$33.25	$33.30
Purchase #5	$215.37	4.790%	$225.6862	$225.69	$225.70	$225.70
Purchase #6	$136.37	7.864%	$147.0941	$147.09	$147.10	$147.10
Purchase #7	$205.30	7.544%	$220.7878	$220.79	$220.80	$220.80
7 purchase totals =	$986.02		$1,050.6273	$1,050.62	$1,050.65	$1,050.70