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	$34.61	10.509%	$38.2472	$38.25	$38.25	$38.20
Purchase #2	$178.77	3.559%	$185.1324	$185.13	$185.15	$185.10
Purchase #3	$188.41	3.264%	$194.5597	$194.56	$194.55	$194.60
Purchase #4	$189.93	12.108%	$212.9267	$212.93	$212.95	$212.90
Purchase #5	$31.26	5.185%	$32.8808	$32.88	$32.90	$32.90
Purchase #6	$234.30	4.570%	$245.0075	$245.01	$245.00	$245.00
Purchase #7	$85.48	11.550%	$95.3529	$95.35	$95.35	$95.40
7 purchase totals =	$942.76		$1,004.1072	$1,004.11	$1,004.15	$1,004.10