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	$169.45	8.403%	$183.6889	$183.69	$183.70	$183.70
Purchase #2	$215.62	12.490%	$242.5509	$242.55	$242.55	$242.60
Purchase #3	$10.71	12.184%	$12.0149	$12.01	$12.00	$12.00
Purchase #4	$56.93	12.551%	$64.0753	$64.08	$64.10	$64.10
Purchase #5	$77.69	10.592%	$85.9189	$85.92	$85.90	$85.90
Purchase #6	$215.42	3.496%	$222.9511	$222.95	$222.95	$223.00
Purchase #7	$165.74	13.787%	$188.5906	$188.59	$188.60	$188.60
7 purchase totals =	$911.56		$999.7906	$999.79	$999.80	$999.90