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	$177.98	7.275%	$190.928	$190.93	$190.95	$190.90
Purchase #2	$167.79	10.858%	$186.0086	$186.01	$186.00	$186.00
Purchase #3	$81.35	9.731%	$89.2662	$89.27	$89.25	$89.30
Purchase #4	$235.69	10.567%	$260.5954	$260.60	$260.60	$260.60
Purchase #5	$93.38	6.832%	$99.7597	$99.76	$99.75	$99.80
Purchase #6	$188.52	12.370%	$211.8399	$211.84	$211.85	$211.80
Purchase #7	$33.74	3.549%	$34.9374	$34.94	$34.95	$34.90
7 purchase totals =	$978.45		$1,073.3352	$1,073.35	$1,073.35	$1,073.30