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	$136.87	10.755%	$151.5904	$151.59	$151.60	$151.60
Purchase #2	$29.60	5.591%	$31.2549	$31.25	$31.25	$31.30
Purchase #3	$47.26	8.651%	$51.3485	$51.35	$51.35	$51.30
Purchase #4	$78.96	8.584%	$85.7379	$85.74	$85.75	$85.70
Purchase #5	$73.47	6.720%	$78.4072	$78.41	$78.40	$78.40
Purchase #6	$187.93	13.447%	$213.2009	$213.20	$213.20	$213.20
Purchase #7	$38.62	7.774%	$41.6223	$41.62	$41.60	$41.60
7 purchase totals =	$592.71		$653.1621	$653.16	$653.15	$653.10