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	$205.98	4.534%	$215.3191	$215.32	$215.30	$215.30
Purchase #2	$140.88	3.244%	$145.4501	$145.45	$145.45	$145.50
Purchase #3	$89.84	10.209%	$99.0118	$99.01	$99.00	$99.00
Purchase #4	$186.92	9.555%	$204.7802	$204.78	$204.80	$204.80
Purchase #5	$119.90	12.196%	$134.523	$134.52	$134.50	$134.50
Purchase #6	$130.39	12.742%	$147.0043	$147.00	$147.00	$147.00
Purchase #7	$52.41	7.747%	$56.4702	$56.47	$56.45	$56.50
7 purchase totals =	$926.32		$1,002.5587	$1,002.55	$1,002.50	$1,002.60