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	$81.46	12.850%	$91.9276	$91.93	$91.95	$91.90
Purchase #2	$200.44	7.497%	$215.467	$215.47	$215.45	$215.50
Purchase #3	$16.69	7.341%	$17.9152	$17.92	$17.90	$17.90
Purchase #4	$227.29	12.864%	$256.5286	$256.53	$256.55	$256.50
Purchase #5	$180.46	6.429%	$192.0618	$192.06	$192.05	$192.10
Purchase #6	$131.31	13.263%	$148.7256	$148.73	$148.75	$148.70
Purchase #7	$168.48	4.626%	$176.2739	$176.27	$176.25	$176.30
7 purchase totals =	$1,006.13		$1,098.8997	$1,098.91	$1,098.90	$1,098.90